CHICKENS AND EGGS – CHAPTER 18 by CHRISTOPHER MILLARD

CHICKENS AND EGGS – CHAPTER 18 by CHRISTOPHER MILLARD

I think therefore I'm Chicken

Brains and Membranes

Bassoon Reed Making by Christopher Millard

Chapter 18 – CHICKENS AND EGGS

Matching profiles, shapes and dimensions are critical steps in reed making.  As I argued in Chapter 11 – A Useful Equation – there is a logical balance between volume, mass and compliance.  To satisfy the bassoon’s need for a workable missing conical apex, larger reeds need decreased compliance and smaller reeds need increased compliance.  It’s a simple relationship: more flexibility is required to make a small reed happy, less flexibility is necessary for the larger reed, so we make thicker profiles for Papa Bear reeds and thinner profiles for Baby Bear reeds.  The principles of dialogue, response, resonance and tuning underly this basic relationship between size and flexibility.

Reed design takes on a whole new level of complexity when we discover that different kinds of profiles seem better suited to different sized reeds.  Spines, rails, tips, channels and hearts are all part of our vocabulary and how we visualize our ideal designs.  It seems clear that different profiles seem specifically suited to different shapes and dimensions.  As we experiment and evolve, we juggle back and forth between changing shapes and changing profiles.  Experimentation and an open mind will always lead to new investigations.  Try this, that…soon we are overwhelmed with variables.  But what comes first…the profile or the shape?? To answer this, we need to do a brief dive into an area of reed physics that I’ve not yet addressed.

Diving Board

When I was a young student at the Curtis Institute in the early 70’s, I made weekly pilgrimages to the Academy of Music to hear the Philadelphia Orchestra.  Bernard Garfield’s extraordinary artistry illuminated every passage he played.  The tone was always resonant and warm and proved the perfect vehicle for his sophisticated musicianship.  Though he was not my teacher, I studied his preferred approach to reed dimensions and profiles.  Garfield’s profile included a delineated tip area, a spine, a pronounced heart and thinning of the sides to bring this smaller dimension reed into perfect tuning.

Most of you will have pursued some form of this very standard, heart focused profile.  It’s a really good model and one that made a lasting impression on me.  As the years passed and my own preferences for response, embouchure and tonal character evolved, I began moving to larger reeds with longer tip tapers, eventually eliminating that little area of thickness that we call the heart.  Despite the fact that I was getting better outcomes, I struggled with letting the heart focused profile go. That early imprint nagged at me, like a commandment that I disobeyed with reluctance!!

For years I have assumed that my long tipped, heartless reeds sounded fine because that profile simply works better for the larger dimension reed.  It’s an observation made by many of us who lean to larger reeds.  But I’ve also come to appreciate that the heartless profile works better because of my embouchure and my preferred ‘effort level’ [Chapter 12 – The Goldilocks Dilemma]. Long tip tapers demand a different relationship between embouchure damping and air delivery.  Let me explain.

There is a range of preferences to how we achieve a tapered diminuendo in our playing.  At one end of the spectrum are players whose embouchure, air and reed trims allow diminuendo to be produced by emphasizing reduced air supply.  At the other end of the spectrum are players who tend to use increasing embouchure dampening during a diminuendo and must therefore supply more air support to compensate for the increased inertia in that dampened reed.  Of course, we all experience our dynamic nuances at various points of this continuum; different profiles lean one way or the other.

I hate to make a broad generalization about profile characters – because there are variables that may disprove every assumption – but I think the more we tend to use embouchure dampening for a complete diminuendo the more likely we are to relocate and reduce the ‘heart’ of a profile.  Contrarily, the more we prefer to produce a diminuendo by simple reduction of air supply [and keep a more relaxed embouchure] the more likely we are to emphasize a ‘heart’ forward reed.

Different profiles respond to embouchure dampening and changes in airflow in different ways.  Profiles with a strong backbone [spine] focus their longitudinal structure down the middle of the membrane.  [We can use the word ‘axial’.] Profiles with open, thinner spines transfer structural resiliency to the sides and rails.  These contrasting profiles are inverted images of each other, and each represents a different expectation for the orbicularis oris muscle group.  Though young reed makers initially think in terms of a single pitch range and a single volume dynamic, we learn to visualize how embouchure and air interact with different profiles and adapt to all registers at all volumes.

Bassoon Reed Profiles

Most of my descriptions of the blades of a reed have emphasized the three-dimensional view of membranes as shells containing and responding to standing waves within.  The missing conical apex model is reasonably good at predicting the interaction of volume/size and compliance in designing acoustically responsive reeds.  But let’s branch out here and consider the behaviour of the blades in a simpler two-dimensional context: the idea of the ‘clamped bar’.

Diving boards are a great example.

You can get a really good idea of how length and stiffness effect both amplitude and frequency in a clamped bar.  Take a metal ruler and hold one end on to a table, letting most of the length sit free.  Give it a good “TWANG!”

Fixed Bar Twang

Shortening the free length of the ruler increases the frequency of oscillation because pitch rises and falls according to the free vibrating length of the ruler.  This is a classic example of the elastic properties of a linear object like a reed blade.  There’s a beautiful equation covering these relationships of stress and strength, expressed in Young’s Modulus. Thomas Young [1773-1829] is right up there with Bernoulli in my book.  He’s responsible for the wave theory of light, too.  Smart guy, but never played the bassoon.

When we observe a clamped bar, we are seeing something oscillate at a natural resonating frequency, with no external influences.  As the past 17 chapters have argued, bassoon reed oscillations are primarily controlled by the standing wave within the bore.  Compliance slightly modifies frequency – the flexibility of the cane determines the efficiency with which the pressure-controlled valve operates.  It’s reasonably easy to visualize how the membranes function as servants to the internal bore frequencies – remember trampolines and tympani heads?   But when we shift our attention to the diving board viewpoint – the blades as two-dimensional clamped bars – we see that profile variables influence pitch according to which notes on the harmonic ladder we’re playing [Chapter 13 – Stairway to Heaven]. A deeper look at the metal ruler behaviour will help us in seeing the effect of profiles on the two-dimensional behaviour of a reed blade.

Young reed makers are frequently presented with diametrically opposed observations about how thickness and dimensions influence pitch.  One school suggests that removing cane lowers pitch; the next says that removing cane raises pitch.  If you’ve made enough reeds, you will know that both statements can hold true.  It all depends on other variables.  The acoustics of the reed/bassoon dialogue depend on the interaction between two interacting sets of physical behaviours.  One group focuses on the membrane – ‘shell’ physics if you like – and the other focuses on the blades – clamped bar physics.

Your twanging ruler is a somewhat limited representation of the behaviour of the reed blade because this metal bar has uniform thickness, width and stiffness.  Reed blades are considerably more complex as they have variable width and decreasing thickness from throat to tip, and variable compliance due to internal cane structure.  And never forget – your ruler’s vibrating frequency is not being controlled by a standing wave; its behaviour is entirely determined by its own dimensions!

Twanging metal rulers will be sharper if the steel is thicker, flatter if they are wider, sharper if they are shorter.  But what happens with your ruler when you change its thickness in one specific area?  This is actually quite easy to test.  If you glue/tape a bit of cardboard to the tip of the ruler you will discover the twanging pitch will drop!  Adding mass [front-loading] to the tip of the clamped bar lowers its natural frequency.  Now try adding some material towards the fixed end.  Back-loading mass here will raise the frequency.

Do you see any parallels in your reed trimming experience?  Leaving tips thick will typically tend to lower pitch just as leaving backs thick will typically raise pitch.  Now, while distribution of mass on the clamped bar explains this relationship, remember that much of the complex physics of a reed is governed by the three-dimensional interacting factors of the membrane shell and the internal standing wave.  Nevertheless, this alteration of mass at the tip and its effect on pitch is frequently observed, even though it seems at odds with the behaviour of membranes and shells.

Here is the paradox: while increased membrane thickness as a whole decreases reed compliance and raises pitch, increasing thickness at critical points of the profile can lower pitch.   Furthermore, the pitch effects of front-loading or back-loading mass are exaggerated as we move to higher notes.  A perfectly content reed with an ideal MCA for response in the bass clef is often flat in the tenor range if the tip region is too thick.

These confusing inconsistencies between the sharpening effect of thicker blades and the odd flattening effect of thicker mass at the tip of the reed can drive you crazy.  Implementing the principles of the MCA theory [volume, dimensions and compliance] will get you most of the way to a functioning reed, because the bassoon’s standing wave frequencies tend to dominate the three-dimensional physics of membranes.  But the critical final trimming that delivers a musically flexible reed must be increasingly respectful of the two-dimensional physics of the blades as clamped bars.

Shell physics and bar physics engage in dialogue with the bore in differing ways; the push and pull of their interactions lead us to develop profiles that are comfortable for our individual embouchure and air preferences.

Profiles

Courage in Profiles

So, with apologies to crows everywhere, I pose the question: what comes first – chicken or egg?  In biology this question is rhetorical and circular – each proceeds the other in an infinite cycle.  But in reed making, profiles may indeed come before shapes.  The intuitive, tactile relationship between lips, air and vibrating reed is [like the egg] the starting point.  We incubate and nurture with our embouchures and our shapes and measurements evolve to get the best out of our individual sound production preferences.

In the next chapter, we will look at some of the predictable tonal outcomes when we choose certain profiles.

Chapter 19 – CHIAROSCURO

P.S.  There is a wonderful new book on reed making by the former Houston Symphony bassoonist Eric Arbiter.  It’s an extremely practical and beautifully organized book about many aspects of the reed making craft.  The Way of Cane – published by Oxford University Press.  When my philosophical musings about reed acoustics become overwhelming, Eric’s book illuminates a practical path to finding success in your individual reed making.

Read more about Christopher Millard. Chapter 1 – The Craftsman Chapter 2 – Can you explain how a bassoon reed works? Chapter 3 – Surf’s up! Chapter 4 – The Physicist’s Viewpoint Chapter 5 – The Big :Picture Chapter 6 – We’ll huff and we’ll puff… Chapter 7 – Look Both Ways Chapter 8 – Dialogue Chapter 9 – The Big Bounce Chapter 10 – The Incredible Shrinking Bassoonist Chapter 11 – A Useful Equation  Chapter 12 – Goldilocks’ Dilemma Chapter 13 – Stairway to Heaven  Chapter 14 – Reed MyLips Chapter 15 – Resonance Chapter 16 – Corvids & Cacks Chapter 17 – Lift  Doodles & Design by Nadina

CHAPTER 17 – LIFT  by Christopher Millard

CHAPTER 17 – LIFT by Christopher Millard

Brains and Membranes

Bassoon Reed Making by Christopher Millard

Chapter 17 – LIFT

Those of you who have patiently followed this blog for several months might be longing for some practical information rather than the fanciful analogies about conga lines and trampolines. Sorry, I have one more holistic concept to impart. It’s one that helps me analyze what I feel and hear in the initial trim.

Bi-plane, flight factors, bassoon reed

Little Bassoonist  would love to fly as much as she would love to master the bassoon. She dreams of soaring above the clouds and humming Jolivet. She’s not particular about what kind of plane. A glider will do, or maybe a compact Cessna for those weekend flights. Sometimes she sees herself immaculately garbed as an airline pilot, flying a 300 tonne Airbus, and on those passive-aggressive days – she’d happily pilot a stealth fighter!

Anything to get up in the sky.

Reeds and airplanes are bound by a common thread because they are both dependent on airflow, especially the relationship between air velocity and surface pressure as expressed in the Bernoulli theorem. The typical curved top/flat bottom shape of an airplane wing produces accelerated air flow and reduction in surface pressure on the top wing. The V shape of a bassoon reed causes acceleration of airflow and a continual tendency to pull the blades together.

Thinking about different kinds of planes is a bit analogous to thinking about reeds. Ultralight planes have tiny engines and low mass -something like those effortless Baby Bear reeds that allow us to float with nuance and ease in the third octave. A single engine Cessna is heavier, but it’s still nimble and efficient in the air, like a good flexible Momma Bear recital reed. On the other hand, that big Airbus requires 50,000 HP engines to get off the ground. But they can carry huge loads and go long distances – like the requirement to project a solo passage in a 90 player orchestra.

What are the primary factors to consider in achieving flight? The plane needs enough lift and thrust to overcome the weight of the plane and the drag caused by friction during forward motion. What’s this have to do with reed making? Well, meditating on these factors might help you get your head away from dial indicators, refresh your thinking and get you up off the ground…

4 flight factors, thrust, drag, weight, lift, bi-plane

The factors shown here represent the forces on a plane moving forward through the air. By shifting perspective a bit we can see similar force when air is moving forward through a reed (below).

Bassoon reed, 4 flight factors
The adjustment in this diagram allows us to visualize thrust as the airflow from the player and drag representing inertia and resistance in the reed.

Each of these four factors has a loose counterpart in the dynamics of a bassoon reed.

1. Thrust represents propulsive energy. No problem there – that’s your air supply.

2. Lift represents how a plane leverages airflow to create reduced pressure on the upper surfaces of its wings. In a reed, Bernoulli ‘suction’ continually converts airflow by repeatedly pulling the blade membranes together.

3. Weight is the mass of the airplane plus its contents – pilots, passengers and cargo. In a reed, we can think of this as the static mass of cane that is resisting vibration – dimensions and profile thickness mostly.

4. Drag measures how efficiently the airplane’s external shapes cut through the atmosphere. For us, this might be a measure of inconsistencies in cane structure, profiling asymmetry and embouchure dampening.

In Chapter 16, I described the acoustical behaviour of reeds unattached to bocal and bassoon. As we begin adjusting our reeds, it can help to visualize each of these four interacting factors.

The challenge in writing this ‘philosophical’ blog about reed making is finding concepts and ideas that are inclusive for a broad range of bassoonists. I’m always searching for images and analogies that might illuminate highly divergent individual techniques. Fifty years of reed making has taught me that a very broad range of profiles and measurements can still be brought to the service of the specific tonal and performing preferences of an individual. In other words, I believe that we will always tend to produce the sound we want no matter how we vary our reed designs. We can use a Papa Bear reed or a Baby Bear reed and still achieve our preferred sound.

cane, bi-plane

So, let’s examine the crow from a pilot’s point of view!

Little Bassoonist is dreaming of her cockpit. She is reviewing the manual. This small plane requires her engine to run at 1700 RPM for takeoff and with a normal load she will become airborne at 60 mph. The instruments deliver precise information for a safe and predictable flight. But what would she do without an instrument panel? I expect an experienced pilot might remember the sound of the engine at 1700 RPM and have a visual memory of what 60 mph looks like.

Back at her reed desk, LB is reviewing all the recommended measurements from the manual her teacher has supplied. She has an expensive dial indicator and a sharp profiler blade! The blank in her hands precisely matches all the assigned measurements. Unfortunately for LB, her reed is not a precision piece of technology; it’s wood. No amount of measuring is going to assure her of a good take off. But like that experienced pilot, LB can remember what appropriate air flow feels like.

With the blank in her mouth for the first time, she gently tests out this ‘remembered’ air flow. Is the ‘thrust’ sufficient to initiate vibration? If not, she intuitively increases her air supply until the reed responds, at which point she can start listening for peeping pitch, crow behaviour and additional overblown harmonics. [See Chapter 16]

This a moment fraught with uncertainty for young reed makers, and it’s when all the individual approaches diverge. For example:

  • Is the crow loud and raucous with excessive low frequency components?
  • Is it a tight and sharp peep, unwilling to open into the complexity of a crow?
  • Does it feel strong, resilient and vibrant?
  • Is it stiff like a popsicle stick with very little available vibration?
  • Is the overall challenge to encourage more vibration or to tame too much vibration?

The Weight/Lift/Thrust/Drag model offers possibilities.

  • No matter how efficient its wings or engine, a plane with too much cargo will not get airborne.
  • The aerodynamics of the plane are designed to operate within the parameters of the other three forces. Lift is modified by weight, thrust and drag.
  • Thrust is determined by the power of the engines, which exert forward momentum via the structure of the fuselage. That thrust is attenuated by the weight [mass] of the plane and by the aerodynamics of the wings.
  • Drag is determined by the profile of the body and wings and the resulting effect on wind resistance.

In a bassoon reed we see some analogies.

  •  No matter the contours and dimensions,, reeds with too much mass will resist the Bernoulli process. They are too stiff to allow lift.
  • The profile of a reed is designed to balance structural stiffness with flexible response to air flow and to permit natural embouchure damping.
  • The driving thrust of airflow is controlled by the blowing preferences of the player in any given musical circumstance. The response to airflow is attenuated by thickness [mass] and the aerodynamics of the profile.
  • Drag is associated with lack of plasticity in the cane as well as the effect of embouchure dampening.

 

Sit back and relax

As we begin trimming, we are faced with the decision of how much to take from the front, sides, middle or back. Many bassoonists start with thinning the tip and then move on to the wings. This technique produces thinner cane in the area where the Bernoulli sucking force is most pronounced – where the membranes in their static position are closest together. The typical thin tip/weak wings/heavier heart profile serves the aerodynamic efficiency for air entering the reed.

I think removing cane is an often-misunderstood process. Always ask, “When I scrape cane in a specific spot will I increase or decrease vibration?” For example, removing cane at the center point of the tip increases amplitude because it ‘leverages’ the prime area for mechanical response to air. But removing cane at the tip corners will usually weaken the membrane and reduce potential vibration. The outcome depends on whether the adjustment primarily enhances the ‘aerodynamics’ of internal flow or weakens the structural integrity of the membrane as a whole.

Aeronautical engineers are skilled at creating strength while reducing mass. Metallurgical advances have produced metal composites that optimize balance between rigidity and flex. Millions of years of evolutionary advances have produced in Arundo donax sufficient longitudinal and radial strength to grow 20 ft tall and withstand all weather. But the cane would much rather be in the field than stuck on a bassoon!

  • Longitudinal strength in an airplane fuselage is essential to staying aloft.
  • Longitudinal strength in a reed is essential to staying up to pitch.

Regrettably for us, at the granular level cane is highly inconsistent. We typically find areas of mushiness unevenly distributed between the strong vascular bundles that give the blades rigidity. Softer materials vibrate with less resiliency and at slower frequencies, so they correlate to ‘drag’.

Bernoulli-initiated lift is not the only force that allows airplanes to fly, but it’s the one that seems to apply to bassoon reeds. Here are some points of comparison:

  • Reduced pressure on the upper surface of a wing lifts the entire plane. That force depends on sufficiently stable connections where wings meet fuselage.
  • The big variable in the operation of an airplane is the weight of passengers and cargo.
  • Reeds with too much wood in the back are analogous to an overloaded plane; they’re both going to require increased thrust to compensate for weight.
  • Reeds with too much wood in the tip – front loaded – are like airplanes with poor aerodynamic design in the wings requiring extra airflow.
  • Commercial aircraft have to be careful about the distribution of load. If a half full plane seats all the passengers in the front row the plane will keep its nose down, require more power to lift off and present more drag.
  • Reeds need care in the distribution of load. Too much cane in the tip inhibits Bernoulli lift, lowers the pitch [especially in the higher operational modes] and will be a drag to play…
  • The backbone of a plane is the airframe within the fuselage. It requires a careful balance between strength, weight and flexibility.
  • The backbone of a reed, though often presumed to be the ‘spine’, is a more complicated balance between the longitudinal resilience of the fibres, the cellular structure [at the molecular level], the original radius of the plant and the leverage exerted on these factors by the structure of the tube.
  • Flaps and flexible wings are necessary to manage changes in speed and altitude. Flight efficiency is a dynamic process as conditions evolve.
  • Flapping, flexible wings in reeds are necessary to manage changes in musical dynamics and registers.
  • Airplanes don’t fly at fixed altitudes. They must be capable of more thrust and lift at takeoff, and then find cruising altitudes that are more efficient and economical. Pilots adjust wing shapes [flaps] to adapt to these differences.
  • Bassoon reeds don’t operate in single notes or registers. They must be capable of more lift during attacks and be able to climb the ladders from fundamental to register to 2nd harmonic notes, 3rd harmonic tenor register and on up into the wild blue yonder of the altissimo register. Bassoonists constantly adjust membrane shapes to adapt to these differences.

So, what’s the point of all these comparisons?

I like to think of the two blades of the bassoon reed, interacting in reasonably balanced fashion, as small airfoils. Stretched and extended over lengths approaching 30 mm and maximum widths of 15 mm, these singular membranes are profiled to deliver aerodynamic response unique to the preferences of each player. All of these analogies to flight are a way to focus our attention on the ‘input response’ behaviour outlined in my earlier blog chapters, just as my trampoline analogy focuses on the ‘output response’ to standing waves within the bore.

Flight Cane 2

Cane Plane (from the Archives of the Imagination)

As you think about whether these unusual models have any relevance to your reed making, I’d ask you to begin considering a really important question which I’ll take up in the next chapter. “Should we adapt our profile preferences to match our shapes or match our shapes to suit our inherent profile preferences?”

Chapter 18 – Chickens and Eggs

Read more about Christopher Millard. Chapter 1 – The Craftsman Chapter 2 – Can you explain how a bassoon reed works? Chapter 3 – Surf’s up! Chapter 4 – The Physicist’s Viewpoint Chapter 5 – The Big :Picture Chapter 6 – We’ll huff and we’ll puff… Chapter 7 – Look Both Ways Chapter 8 – Dialogue Chapter 9 – The Big Bounce Chapter 10 – The Incredible Shrinking Bassoonist Chapter 11 – A Useful Equation  Chapter 12 – Goldilocks’ Dilemma Chapter 13 – Stairway to Heaven  Chapter 14 – Reed MyLips Chapter 15 – Resonance Chapter 16 – Corvids & Cacks Chapter 17 – Lift Chapter18 – Chickens & Eggs Doodles & Design by Nadina

 

 

Brains and Membranes by Christopher Millard – Chapter 16 – Corvids and Cacks

Brains and Membranes by Christopher Millard – Chapter 16 – Corvids and Cacks

Brains and Membranes

Bassoon Reed Making by Christopher Millard

Chapter 16 – Corvids and Cacks

As if holding a bassoon weren’’t funny enough, we seem to get an inordinate number of laughs just testing our reeds.

We all ‘crow’ on our reeds – but to what end? What are we looking for? Rattles, peeps, honks, caws, croaks, cackles, rasps…squawks??

Time for a quick review. Remember that in a coupled system [bassoon + reed] there are strong bore resonances which determine the periodic oscillations of the input device. But how long does that bore need to be to exercise control? The shortest bore we use is open F; it’s the last rung of that fundamental first ladder from Chapter 13. Upper register notes are based on longer bore lengths, utilizing higher harmonic resonances, which are corrected for tuning by employing complex fingerings.

We can make an even shorter coupled system – just the bocal and the reed. Most of us play on setups where this combination delivers between C3 and C#4. The internal volume of the bocal has its own standing wave behaviour that dominate the reed’s frequencies and creates its own fundamental and harmonics.

Here is a spectrum graph showing what’s contained within that short bocal/reed system. You’ll see similar graphs for any of the notes on that first harmonic ladder.

 

Everything makes sense. It’s sounding 270hz [between a C and C#] which is quite typical for this combination.  The harmonics are all true to the harmonic series.

If we were to start cutting the bocal shorter and shorter at its large end – admittedly a rather expensive experiment – we’d find the sounding pitch getting higher and higher.  Eventually, we’d toss that last bit of metal tube and have the reed all on its own.  By shedding all the expensive parts, we’re left with the world’s smallest bassoon.  And as long as you blow gently, you will get a fundamental and harmonics by peeping on the darn thing.  This next graph shows an analysis of the harmonic components of the simple peeping sound from the reed by itself.

Amazing eh? A functioning coupled system created with a little bit of cane, wire and string. The first harmonic at H1 is 370 hz [F#4] and the next 3 strong harmonics are at 740 hz, 1120 hz and 1480 hz. Simple integer multiples indicate a pure harmonic series.

Now, as we all know too well, as soon as you start blowing a bit harder something strange emerges. We call it a crow. It’s actually a completely separate acoustical phenomenon – a multiphonic. Yes, just like the fancy multiphonic fingerings utilized in some contemporary music but without all those difficult cross fingerings.

So, what’s going on with this cackle? Let’s take a look. Here is the same reed [shown above in its peeping state] but this time ‘overblown’ into a multiphonic crow:

As you can see, there is still some residual evidence of the original peeping fundamental at H1 and H2, though lowered in pitch a bit. But look at all the other components. H3=1020 hz and H4=1360 hz point to further disorder above. These upper frequencies don’t fit into the integer calculated harmonic series, and they are highly unpredictable. Repeated tests of the spectrum of a crow gives a huge range of variability in these higher inharmonics. This volatility is entirely expected due to the extremely weak bore resonance for the internal volume of the reed alone. The resonances for this tiny volume are too weak to adequately dampen and control the very broad range of frequencies ‘contained’ within the reed membranes. So, the peeping pitch is easily overblown, creating wild non-harmonic components. The ‘crow’ is born.

My kingdom for a rooster.

Continued blowing, especially with newer reeds, often reveals yet a third state with the emergence of an ugly CACK, breaking up the multiphonic itself. You can overblow what is already overblown!!

The next graph shows the same reed, but now operating in this rather pathetic third state.

A different primary frequency has jumped out, H1=540 hz, a quarter tone sharp C5. This bears no relation to the reed’s original peeping pitch whatsoever; it’s just a strong natural frequency for the membranes themselves. Additionally, the other components from H2 thru to H6 don’t fit a harmonic series. Not until the very strong H7=1080 hz do we get a 2nd true harmonic [and another at 3240 hz] of the CACK frequency. And because all of these components remain undampened by strong standing waves they are more subject to frequency alterations caused by blowing pressure. When the reed is unattached to the strong bore resonances of a bassoon IT’S THE WILD WEST!!

So, we start with something predictable [the peeping pitch] and move to the crow [mostly multiphonic] and then often a third kind of wild behaviour. What does it all mean?

You will recall that early on in this blog I referred to a general misunderstanding of the crow. I referred to the assumption that the bassoon magically transforms cackling crows into all the notes on the bassoon. I’m hoping that the earlier chapters explaining the bassoon/reed dialogue has persuaded you to think of sound production as a two-way process.

Is there an ideal crow?

Different players look for different multiphonic mixes, and even within an individual’s reed box there will be considerable variety. Crows can reveal to the bassoonist how likely each reed may respond to certain aspects of the bassoon’s acoustical needs. We learn empirically how to associate certain crows with certain outcomes. Big, complex crows are typically indicators that a reed will be strong in the bottom end and have a large dynamic range. Small, simpler crows are usually associated with softer sonority, reduced dynamic range and limited character.

Different sizes of reeds require different peeping and crow behaviours. Larger dimension reeds typically have less overall compliance and will peep at a higher fundamental frequency. Smaller reeds tend to have greater overall compliance and need to peep at a lower fundamental. The character of a crow is associated with membrane profiles, which are themselves optimized to reflect the physical dimensions of the reed.

Remember that in the MCA model size is modified by compliance. Peeping pitches also reflect that relationship. Your narrow reed may peep at a D, my wider reed at an F# – yet both fulfill the formula for the missing conical apex. Equally important, each player’s comfort zone in terms of combined embouchure and air effort will lead them to choose higher or lower peeping pitches.

The variability of reed dimensions and of performers’ physiological preferences suggest that there is no correct crow. There is an unpredictable relationship between crow and bassoon tone that can frustrate expectations. We are often surprised by what we get when we begin to play. Sometimes a crow just reveals how well that reed crows… Have you noticed that a reed crow will vary according to who is playing it?

Over the years I’ve had students call to crow on a reed over the phone [more recently by video chat…]. But it’s very difficult to analyze while someone else is doing the crowing. We need to be the one doing it – sensing the resistance, placing the lips, opening up our oral cavities. Testing a crow is all about the real-time process of producing those multiphonics – what your breath and your embouchure do to create your crow.

So here is my simple advice. Analyze your crows not only by what you hear, but also by what you do to make the crow happen.

Next week in Chapter 17, we’ll look at how to utilize our understanding of input response and how crows can illuminate the mechanics of membrane behaviour and reveal input response. We might also touch upon the acoustical implications of shaping the oral cavity.

 

Read more about Christopher Millard. Chapter 1 – The Craftsman Chapter 2 – Can you explain how a bassoon reed works? Chapter 3 – Surf’s up! Chapter 4 – The Physicist’s Viewpoint Chapter 5 – The Big :Picture Chapter 6 – We’ll huff and we’ll puff… Chapter 7 – Look Both Ways Chapter 8 – Dialogue Chapter 9 – The Big Bounce Chapter 10 – The Incredible Shrinking Bassoonist Chapter 11 – A Useful Equation  Chapter 12 – Goldilocks’ Dilemma Chapter 13 – Stairway to Heaven  Chapter 14 – Reed MyLips Chapter 15 – Resonance Chapter 16 – Corvids & Cacks Chapter 17 – Lift Chapter18 – Chickens & Eggs Doodles & Design by Nadina

 

 

Brains and Membranes by Christopher Millard – Chapter 15 – Resonance

Brains and Membranes by Christopher Millard – Chapter 15 – Resonance

Brains and Membranes

Bassoon Reed Making by Christopher Millard

Chapter 15 – Resonance

In previous chapters, I’ve presented a different interpretation of the term ‘response’.  It’s the idea of a two-way dialogue between bassoon and reed.  Let’s shift our attention to another word that has a big impact on our reed making: resonance.

The Latin word resonantia [echo] stems from the word sono, meaning sound.  So ‘re-sound’ -which makes sense to modern musicians, who think of the prolongation of sound through reverberation.  A resonant hall, for example. Resonance in speech is additionally enhanced by the action of the resonating chambers in the throat and mouth.  Resonance in human relationships describes mutual understanding or trust between people, a form of ‘rapport’.  These are all subjective – and meaningful – uses of the word ‘resonance’.

But resonance has a more objective meaning which we see in physics:

A vibration of large amplitude in a mechanical or electrical system caused by a relatively small periodic stimulus of the same or nearly the same period as the natural vibration period of the system.

In musical instruments, resonance occurs when a vibration of large amplitude is produced by a small vibration occurring at the natural frequency of the resonating system.  This is a pretty clear description of how bassoons react to reeds, isn’t it?  Small amplitude oscillations – like the relatively small vibrations in the reed membranes – sustain a much larger amplitude standing wave in a bassoon bore.

resonance, conch

Little Bassoonist hears the resonance in a seashell…

LB, tiny again, climbs back inside the cavernous bassoon reed and watches the flapping membrane activity above and below her.  It all seems enormous to a miniature bassoonist, but the actual movement of the cane is very small – displacements of less than a millimeter.  And yet, a 2.5-meter bassoon bore, with complex bore resonances pumping out over 90db of sound energy, is all being driven by these very small membrane oscillations.  This is resonance.

At the small end of the bassoon, periodic variations in pressure control the frequency of the reed oscillations.  When efficient input response to airflow matches the output response of cooperative membrane compliance, the coupled bassoon/reed system achieves ideal sonority.  Minimal energy supply achieves maximum acoustical efficiency.   This is resonance.

Resonance is getting more tonal ‘bang for the buck’.  Resonance happens when the MCA value of the reed creates the most in tune collaboration.  Resonance occurs more easily for a Papa Bear reed at the expense of increased effort; with a Mama Bear reed in the right register and sensitive air supply; and for a Baby Bear reed when embouchure can be relaxed sufficiently.  Resonance, in both its subjective and objective definitions, happens when appropriate tuning meets comfortable embouchure and air behaviour.  Resonance is the result of fruitful acoustical dialogue between standing wave and reed – when that faithful partner complies willingly.

Sometimes the simplest ideas reveal deep wells of meaning. 

In the study of bassoon reed making, the idea that tuning and tone are inextricably linked reveals a path to better outcomes.

Here is a spectrum analysis showing the relative energies of the component harmonics in a single note.  It’s a snapshot of C3 [in the bass clef staff] that I measured on one of my bassoons.  On this graph, the vertical axis represents the strength of a harmonic component and the horizontal axis represents its frequency.

Just as spectral analysis of light reflected off a distant object can tell us what elements it contains, so spectrum analysis of sound reveals what component frequencies it contains.

You can see above that the energy peaks show very clear harmonic relationships, because the frequency of each peak is a simple multiple of a fundamental.  In this case, the first harmonic [H1] measures 130hz, and the successive harmonics [H2 – H15+] are all logical members of the harmonic series for this note.  Incidentally, you might notice that the fundamental frequency of the note we hear – C natural at 130hz – is not actually the strongest measurable component in the spectrum.  But look at all those strong harmonics at 260hz, 390hz, 520hz, 650hz etc.  They all contribute richly to their fundamental H1 origin.  The reed chosen for the test was particularly compliant and rich in sonority because it was highly cooperative in supplying energy to all these higher harmonics.  It happily adapted its oscillations to the complex demands of the harmonic series for C natural.   Human ears create a strong perception of the fundamental H1 because of the reinforcing alignment and strength of the higher harmonics.  This is a great example of resonance!!  Small membrane activity = extraordinary harmonic complexity.

It’s important to note that graphs like this take a snapshot of the average harmonic components in a sustained bassoon tone.  They don’t reveal much about the more ephemeral and transient inharmonics, frequencies that are present in the attack of a note and pop up for brief moments throughout a long tone.  Inharmonics are not members of the harmonic series family, but they still contribute to the character of the sound.  As we will see in a later chapter, inharmonics are particularly relevant at the beginnings of notes.

Most of the sound energy in this graph is produced by the first 6 harmonics, but you can also see the significant contribution made by higher frequency components.  When a bassoon/reed coupled system is in a particularly resonant condition we tend to see more energy in the first few harmonics.  The bore resonances of the bassoon are asking for cooperation from the reed across a multitude of component harmonics.  When things go well, less blowing energy produces amplified standing wave behaviours.  This is resonance. 

Our little bassoonist is not sure what to make of all this information.  She just wants a good sound and to be reasonably in tune.  Of course, it’s the tuning itself that gives good sound.  We tend to use the word ‘tuning’ to describe sharp or flat, but I prefer a much broader definition that incorporates some of the ideas of the MCA concept.  A well-tuned engine runs efficiently; a well-tuned reed maximizes resonance because it is acoustically efficient.

Like many young bassoonists, LB often winds up playing quite sharp.  But she should take note that there’s a surprising maximum upper limit to her sharpness.  It’s quite difficult to play at A=446hz because a bassoon engaged in an acoustical dialogue with a small, stiff reed will only bend its natural resonances so much before the system is hopelessly compromised.  The native natural bore frequencies of a well-designed bassoon prefer to have their way.  Bassoons are carefully set up to work efficiently [with resonance] at either A=440hz or A=442hz.  Undersized MCA value reeds will sharpen the intonation, but the bore resonances quickly rebel.  Sonority quickly gets very unpleasant and very uneven. The distortions are not equally distributed throughout 3 octaves either.  Those 3rd and 4th harmonic ladder areas in the tenor range and above will sharpen significantly more than their ancestor 1st and 2nd harmonics.  Inertia increases with higher frequency oscillations.  The flow of acoustical dialogue diminishes and sonority is compromised. Resonance is lost.

So, what about flatter reeds? I have to confess one of my life-long goals was to achieve the resonance that a A=438hz setup delivers so easily, but somehow still operate in a 440/441 orchestral environment.  Flat reeds usually have sufficiently large MCA values to allow the bassoon to find all those cooperative resonances, but there are physical challenges involved in constantly supporting ‘from below’.

Designing and trimming reeds is primarily a process of finding an average pitch centre that serves to maximize resonance while optimizing embouchure and air preferences.

Looking back at 46 years of orchestral work, I know that balancing my own sound aspirations with reasonably balanced embouchure and air support remains a life-long quest.

 

LB asks a really important question: should she play slightly sharper reeds and relax down into the work pitch of her colleagues, play slightly flatter reeds and hold up her pitch with more effort, or play reeds that are perfectly balanced and comfortable, delivering optimal resonance with sensible demands on embouchure and air?

If you like that third answer, congratulations.  And best of luck.  Most of the time you are going to be dealing with one tendency or the other.  You need to be aware of the benefits and drawbacks wherever your fine tuning takes you.

LB is remembering her visit to the Bears’ House.  She couldn’t choose just one reed, so she took all three.  Now she’s experimenting with the relative comfort and effort the three reeds demand.  Like most bassoonists, LB is remarkably clever, and has come up with a way of evaluating her Bear reeds.

This is how LB is thinking about her Bears and their reeds, lines A, B and C.  Line D represents her own particularly crappy reed that she can’t seem to fix.

The graph x axis represents the ascending registers of the bassoon.  The y axis represents ‘Effort’, a theoretical ‘mash’ of embouchure and air.  The idea is that the plotted lines represent the change in workload.  The steeper the curve, or the higher its placement, the more effort is required to produce resonant sonority all the way up to the high end. 

Take a look and think of your own reeds.  Do some of them remind you of line A?  [Probably larger MCA values, more Papa Bear style?].  Does line C make you think of stuffy, sharp reeds that nevertheless give you a better shot at high D’s?  Perhaps most importantly, do you think the measurement of your work level could be plotted in a fairly straight line??  This is really important: the idea of response linearity [as in predictably even]. Line D has a big curve going up, which describes a reed that is okay until it reaches the tenor range, at which point the embouchure and air effort becomes relatively more demanding.

On the grid

Linearity is a concept that’s quite universally appealing in both instrument design and reed making.  For LB, it’s a way of describing a comfortable climb up the ladders in her Stairway to Heaven.

Next chapter, we’ll look at Crows, Roosters, Ravens and other Multiphonics.

Read more about Christopher Millard. Chapter 1 – The Craftsman Chapter 2 – Can you explain how a bassoon reed works? Chapter 3 – Surf’s up! Chapter 4 – The Physicist’s Viewpoint Chapter 5 – The Big :Picture Chapter 6 – We’ll huff and we’ll puff… Chapter 7 – Look Both Ways Chapter 8 – Dialogue Chapter 9 – The Big Bounce Chapter 10 – The Incredible Shrinking Bassoonist Chapter 11 – A Useful Equation  Chapter 12 – Goldilocks’ Dilemma Chapter 13 – Stairway to Heaven  Chapter 14 – Reed MyLips Chapter 15 – Resonance Chapter 16 – Corvids & Cacks Chapter 17 – Lift Chapter18 – Chickens & Eggs Doodles & Design by Nadina

 

 

Brains and Membranes by Christopher Millard – Chapter 14 – Reed My Lips

Brains and Membranes by Christopher Millard – Chapter 14 – Reed My Lips

Brains and Membranes

Bassoon Reed Making by Christopher Millard

Chapter 14 – Reed My Lips

As our Little Bassoonist climbed the ladders into the high register she found herself thinking about the adaptations she makes in the upper register. Her teacher often reminds her to increase air support as she ascend; scaling ladders and scaling registers both demand effort. We usually think supplying faster air or more ample air is an important part of ‘holding up’ the pitch of the upper registers. I’m going to present a slightly different take on all this.

Balance, Bassoon Reed Physics

Unless our reeds are too sharp [Baby Bear!] and stuffy, it’s usually not a problem to get a lot of sound in the lower fundamental register. In fact, most reeds with optimal compliance produce more sonority at the lower end and less at the top. The bassoon is a bottom-heavy instrument. Flutists, who struggle with the bottom octave, are frequently jealous of the ease with which we can honk out low Bbs, though flutists have a relative advantage in the upper octaves.

LB’s teacher demands she practice her scales with a bit of crescendo in the ascent and a corresponding diminuendo in the descent. This guidance isn’t because ascending phrases always require expressive growth or descending phrases always require diminishing tone, although that is frequently appropriate. Rather, the habit of adding more support in an ascending passage is a strategy to correct the imbalance inherent to bassoons: loud and edgy at the bottom and squeezed at the top.

Chapter 13 examined the acoustical reasons for this diminishing sound profile.Each step to a higher register is achieved by eliminating a strong lower harmonic; sonority can suffer as we optimize the remaining higher frequency resonances. Increased embouchure damping reduces the richness of sound by reducing the cumulative energy of these remaining harmonics. Even modest damping changes the contours of the membranes and thereby increases inertia. As we move to higher frequencies, the slight closure of the reed not only alters the MCA value but changes how the blades respond to the Bernoulli effect. Tenor register pitches in particular become less responsive to nuance and articulation.

How does our little bassoonist respond to this? By increasing air supply. Mimicking a crescendo during an ascending scale compensates for the reduced amplitude of the reed membranes. If we must lose the 1st and 2nd harmonics and all their energy, we need to rebalance input air supply simply to maintain the impression of even dynamics.

 

LB is sometimes confused by these discussions. The balance between air support and embouchure can be minefields in the pedagogy of both playing and reed making. She aspires to play in the third octave by moving the air faster, but she sometimes expects too much. Most reeds required a bit of help from the lips.

I think we can take some reassurance from the laddered acoustics that I outlined in Chapter 13. Ascending the registers demands a certain amount of embouchure damping which needs an increase in air supply to compensate. I’ve seen many young players get into throat and upper body tensions by over-reliance on air as the only tactic for holding up the upper register. I’m not necessarily advocating for larger MCA value reeds – effortless reeds are deeply appealing!! But embouchure serves a critical role in climbing the ladders. Reed making demands adaptation to the changing conditions of cane, weather, repertoire, performing environments and our emotional state. Respecting the physics will lead to better strategies in solving our reed challenges.

laddered bassoon accoustics

Chapter 10 saw our little bassoon character inside a huge, imaginary reed.

Climbing back inside, LB observes in slow motion the blades flexing. There are changes in the overall shape of the membranes as the player moves from low register to high register. In addition to an observable reduction in the aperture gap, she sees a reduction in the flapping motions in the wings. This concave collapse of the wings results from increased embouchure pressure, which transfers into these wider, thinner areas of the membranes. When blades are held a bit tighter, larger motions are restricted and help dampen the lower harmonics as well as move the reed into a Mama Bear or even Baby Bear dimension.

 

 

Wider flexing motions feed the lower harmonic standing waves for any bore length. Our typical reed profiles encourage functional concavity in the wings, reducing the amplitude of lower frequency vibration. Damping those wider motions reduces the lower harmonics in the dialogue. This strategy of damping the lowest available modes helps the reed more efficiently supply energy when we are utilizing higher bore resonances. As we climb the ladder past the 2nd harmonic area and up into the tenor range the embouchure, plus the manipulation of half-holes, vents and cross fingerings, helps eliminate the 1st and 2nd bore harmonics and allow for control in the upper range of the bassoon. My Chapter 12 assignment demonstrates this behaviour with all but the most extremely light reeds. You played the reed with your lips over the 1st wire and observed what happens as you climb the ladders. The pitches may continue to operate up into C4, but you will almost certainly find the bassoon reverting to its lower modes and sounding like a dying porpoise.

If you go back to the lips over wire exercise I suggested in Chapter 12, you will no doubt realize that if you blow REALLY hard, you can indeed extend the operation of the bassoon well up into the top of the third octave. It just takes a heck of a lot of air.

Repeating the experiment with lips on the reed but with only enough embouchure to seal the air will have taken you a little bit further – depending on how light your reeds are. But rather instinctively, we tend to dampen the embouchure and increase air support as we ascend.

But….

LB remains slightly confused. Surely, she thinks, accelerated air supply must have an effect on pitch!? And indeed, it does.

Air speed

This is a very confusing phenomenon, because in other instruments excessive volume tends to lower pitch. We see this flattening effect in the clarinet when it’s overblown. However, the bassoon will usually sharpen with increased air flow. We see this in vibrato production when the intermittent acceleration of air several times a second not only causes repetitive increases in volume but also in pitch. Sufficient air flow into a bassoon reed will also sharpen the upper bore resonances, and at an exaggerated rate! In fact, the intonation effects of embouchure and air increase substantially as we move into higher bore resonances. That’s why vibrato is so hard to temper up high, and pitch bending in the high register can be so extreme. The physics are elusive, but we presume that increased air velocity through the aperture must raise the natural frequencies of the membrane ‘shell’ as well as cause greater inward displacement of the blades and decrease that theoretical missing conical aperture. So, there’s absolutely real physical reasons why air speed might sustain both register and pitch. The evidence is with us constantly.

Next week, in Chapter 15, we are going to explore Resonance. It may not be what you think…

Read more about Christopher Millard. Chapter 1 – The Craftsman Chapter 2 – Can you explain how a bassoon reed works? Chapter 3 – Surf’s up! Chapter 4 – The Physicist’s Viewpoint Chapter 5 – The Big :Picture Chapter 6 – We’ll huff and we’ll puff… Chapter 7 – Look Both Ways Chapter 8 – Dialogue Chapter 9 – The Big Bounce Chapter 10 – The Incredible Shrinking Bassoonist Chapter 11 – A Useful Equation  Chapter 12 – Goldilocks’ Dilemma Chapter 13 – Stairway to Heaven  Chapter 14 – Reed MyLips Chapter 15 – Resonance Chapter 16 – Corvids & Cacks Chapter 17 – Lift  Doodles & Design by Nadina