Brains and Membranes by Christopher Millard – Chapter 10 – The Incredible Shrinking Bassoonist?

Brains and Membranes by Christopher Millard – Chapter 10 – The Incredible Shrinking Bassoonist?

Brains and Membranes

Bassoon Reed Making

by Christopher Millard

Chapter 10 – The Incredible Shrinking Bassoonist

Our little bassoonist is tired from all that Milde on the trampoline.  Exhausted, she falls into a deep sleep.

And she dreams.  Of Milde, melodic minors and Mozart.  Of straight shapers, cut fingers and dull profiler blades.  She finds herself lying inside a cavernous bassoon reed.  Time is running ever so slowly.  A gentle breeze is flowing into the bassoon cave and she feels the air tingling with undulating pressure waves.  She looks up to see the gently curving arches of the upper membrane, a mirror image of the lower blade on which she sits.  She looks back down the dark tube of the reed into the blackness of the bocal and feels the waves of pressure wash over her.  She turns towards the enormous aperture and feels the slow wind blowing.

Our brave little physicist/bassoonist feels the gentle breeze in her face.  But she is mostly aware of the compression/rarefaction waves behind her – moving at the speed of sound and riding the in-coming airflow like a wave on a river current.

In her dream, time continues to slow.  Cocooned in her enormous shell, she watches the blade membranes undulate as they interact with both the air flow from the player and the complex multi modal pressure waves coming from the bassoon bore behind her.  The bassoon is being played gradually louder and with increased blowing pressure comes an increase in the size of the membrane contortions.

inside a bassoon reed; compression and rarefaction

It’s a fascinating revelation: the dynamic increases the size and severity of the waves’ movement yet the frequency of these motions remains unchanged.

The chaos and asymmetry of the waves is astounding, especially at louder volumes

.

The sound of the bassoon, so warm and reassuring, seems disconnected from the complexity of the membrane functions.  She had expected the graceful curves of a cresting ocean wave.  Instead, she sees alternating convex and concave ripples in the membrane as the top and bottom blades are thrown towards each other, the aperture closing like a slamming door.

The milliseconds tick on.  Our little friend begins to see patterns in this membrane behavior.  It may not be smooth, but the complex irregularities seem to be repeating over and over.  Suddenly, she understands the correlation between the tingling compression waves at her back and the repeating undulations above and below her.

She is standing at the very meeting place of input and output response and bears witness to the marriage of the bassoon and its pressure-controlled valve.

As the dream unfolds, our little friend begins to hear music.  Someone is playing this huge bassoon, with dynamics and nuance, over its three plus octave range. She watches as the membranes respond to intricate control from the embouchure outside.  The compression waves slow down – the low register is asking the membranes to slow down their energy conversion frequencies.  The bassoonist must be relaxing the embouchure, because she sees the membranes open more.

Suddenly, higher pitches dominate and the bassoonist presses into the membranes, creating tension and reducing the size of the cavern.  Le sacre!!!

The dream ends…

This visualization of the internal workings of your reed will be a theme that we return to as we examine the relationship of air, embouchure and musical demands.

The bassoon reed-valve needs tremendous flexibility to accommodate the numerous frequencies – both fundamentals and harmonics – produced throughout the full range of the instrument.  Just as a violin string needs to move simultaneously in both its whole length and in many divisions, the membranes must be simultaneously activated and able to move in wide/narrow patterns of motion and in slow/fast frequencies.  Viewing this action from inside the reed in our slowed-down dream, our little physicist likely observed lower frequency full side to center closures of the tip aperture and at the same time witness higher frequency displacements in narrower bands of the membrane.   The multimodal closings and openings of the valve respond to both the multiple frequencies and the varying amplitudes of pressure that the bassoon requires.

In the next chapter we’ll leave dreams behind and concentrate on some core dimensional principles.

Coming soon,  Chapter 11 – A useful equation

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

Doodles etc by Nadina

i’m having trouble sleeping now

Brains and Membranes by Christopher Millard – Chapter 9 – The Big Bounce

Brains and Membranes by Christopher Millard – Chapter 9 – The Big Bounce

Brains and Membranes

Bassoon Reed Making

by Christopher Millard

Chapter 9 – The Big Bounce

Before we go any further, I want to introduce a new term to your reed making vocabulary – membranes.

It’s a nice, 100% organic word.

A membrane is a pliable sheet or layer – especially of animal or plant origin.

It comes from the Latin membranus,meaning skin.  Skin separates and contains what’s within the body – while remaining pliable, compliant and responsive to our external environment.   Reed ‘membranes’ separate and contain what’s within the bore –  remaining pliable and responsive to that internal complexity as well as the external pressure from our lips.

The walls of the bassoon and bocal are mostly stiff and only slightly responsive to internal vibration.  The top and bottom blades of our reeds are an extension of those walls, but they are highly compliant.  Wood, rubber linings and metal walls give way to the ‘living’ membranes of the pressure-controlled reed valve.

Timpani heads are stretched membranes; indeed, they were originally made from calf skin.   Their vibrational frequencies are determined by variable tension and to a much lesser extent the natural frequencies of the drum they’re attached to.  A timpanist can control the pitch of his drum by altering the internal tensions of the membrane.  This process is at play when we are designing profiles.

Reed membranes share similarity to drum heads [higher tension = higher frequencies] but governed by longitudinal, radial and diagonal elasticity.  Compared to the quite broad pitch flexibility available to the timpanist, bassoonists deal with a much smaller range of frequency adjustments.  The basic pitch is primarily governed by the length of bore.  And while the difference between a very relaxed membrane [a soft, flat reed] and a very stiff membrane [a hard, sharp reed] may only be a quartertone in pitch difference, that small variation presents a universe of heartache.

Using the world membrane helps me to think of the behaviour of reeds in more holistic terms.  I think we waste a lot of time thinking about how individual parts of the reed operate independently.  [You might recall my reference to Mr. Schoenbach’s assertion that different notes came from different parts of the reed?]  Now I’m able to think of each of the two membranes [top blade and bottom blade] as singular entities – stretching, contorting and vibrating in a totally interconnected way.

Have you ever jumped on a trampoline?  Every part of it is interconnected.  There’s no better way of imagining holistic, elastic behaviour.

Reed membrane, reed trampoline, bassoon reed

Practice Milde while bouncing.

The reed pressure valve has a primary function – to modulate airflow by closing and opening. The two membranes [top and bottom blades] respond to the motion of air from our lungs.  This ‘input response’ governs our need to design membrane profiles that are thinner at the tip and the sides, in order maximize and leverage the conversion of airflow into periodic vibration.

The idea of first blowing the reed closed is critical to understanding why we profile as we do. For the membranes to bend inwards they require the selective flexibility achieved by our approaches to profiling: the Bernoulli effect increases with air velocity, so it’s most pronounced where the gap between the membranes is minimal.  Therefore, we profile the membranes to be more flexible in those regions, which explains the universal tendency to make tips and sides thinner than backs and centers.

We can’t make an attack if the tip is too thick.  There is an immediate functional connection between thin tips and input response: the membranes must come together willingly to begin the dialogue between airflow and vibrating bore.

The mechanics of input response are governed by relative tensions of the membranes – from side to center, front to back and diagonally.   All are connected at a cellular level.  The combination of profile and internal structure determines how efficiently the reed responds to the Bernoulli force, both initiating and maintaining the sound.

Jumping on trampolines is actually a pretty useless way to learn Milde.  But, it’s a great model for visualizing some of what reed membranes actually do. 

If bassoons produced simple sine wave sounds with no harmonics, the reed/membrane/trampoline/timpani analogy would be really easy to visualize.

But acoustic musical instruments all include sound profiles with rich harmonics.

Reed membranes that are happily compliant with a specific harmonic tend to be compromised in unexpected ways by other harmonic components.  I’ll explain…

If you are still jumping on that trampoline, consider this: there is usually a very large area that gives you good lift.  Trampolines become less efficient as you move to the edges, but they remain accommodating to all kinds of bouncing.  But the minute a second person joins you the behavior of the trampoline becomes more complex.  Imagine you have a dozen people bouncing: everyone’s bounce impacts the sweet spots for everybody else.  If you all coordinate your jumps at a single frequency you can effectively manage the trampoline’s elasticity.  But if you all have independent jumping frequencies, the sweet spots are not evenly distributed, creating chaotic uncertainty about each individual’s bouncing success.   

Our trampoline bouncers include very slow jumpers with large mass and slower bouncing preferences, average size jumpers with average size preferences and little, itty-bitty, fussy tiny ones with very high frequencies.  The trampoline membrane has to make sense of all this – slower fundamental harmonics all mixed up with faster overtone harmonics.  All this jumping starts to assume a repetitive character.

The fattest bouncers are happy to jump at 55hz, their close friends choose to bounce twice as fast [110hz] and their relatives bounce three times as fast [165hz] and their children like to go four times faster [220hz]. 

So imagine each jumper represents a specific bouncing frequency in the complex sound waves within the bore.  The compression-rarefaction waves that the bassoon naturally likes to utilize are all pushing and pulling on the internal membrane surface, vying for energy and reinforcement.  Different frequencies ask for different modes of flexing within each membrane; slower and wider flexing for the fundamental and quicker, more narrow flexing for higher harmonics.  This describes output response, i.e. the membrane complying with the acoustic needs of the bassoon itself.

I can go back several paragraphs and repeat almost word for word: The mechanics of output response are governed by the relative tensions of the membranes.  The combination of profile, cane resiliency and internal structure determines how efficiently the membranes comply with the internal acoustical forces, both responding to and reinforcing the vibrational frequencies within the bassoon.

There you go, a trampoline membrane operating as a musical instrument with a fundamental and a family of harmonics.

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

Doodles etc by Nadina

 

reed drum dum dum

is this what you meant??

Brains and Membranes by Christopher Millard – Chapter 8 – Dialogue

Brains and Membranes by Christopher Millard – Chapter 8 – Dialogue

Brains and Membranes

Bassoon Reed Making

by Christopher Millard

Chapter 8 – Dialogue

Bassoon reed, huff, puff

You must be wondering if I’m ever going to tell you anything of immediate value – like how to build blanks, profiling, details of shapes or measurements? 

Later. 

Right now, let’s keep focusing on holistic concepts.

So, how about a nice easy subject?  Like ‘response’?

Uh-oh….

Have you ever noticed that the word response – when applied to anything but reed making – is usually used in the context of dialogue?  It’s usually about feedback to a spoken or written thought, a reply to a question or an acknowledgment of a communication. Here are some synonyms for response: rejoinder, retort, comeback, counter and riposte.  These are all ripe with meaning.  Dialogue in conversations are typically complex and can be guided or controlled by either party.    

If you are speaking with someone who absolutely won’t respond, we have a rich set of internal observations, which lead us to figure out why the conversation is one-sided. For example, is there a physical reason? Are we mumbling, is there hearing impairment, is there too much ambient sound, too much distraction? Perhaps there is a different language, or little shared experience?  Is there a complex emotional barrier?  Are we too aggressive, too timid, overbearing or our relationship poisoned by personal history?   Conversations easily become unbalanced, with one party controlling the evolution and outcome of the interaction.

To communicate effectively, we need to sort out the reasons why dialogues become one-sided.

Can you see where I’m going with this? 

Response is this big catch-all term to describe the behaviour of reeds in the context of our dialogue with the music.  For example, we say a reed is responsive if…

  • Vibration begins with a predictable and efficient input of air…
  • Tonal changes in dynamic and colour can be achieved with a comfortable amount of embouchure effort and blowing pressure

Then we might start going for comparative details…

  • Tchaikovsky 6 or Le Sacré are equally cooperative
  • Low Bb ff staccato is as immediate as a gentle mid range mp attack
  • The reed allows flexibility in tuning with fellow performers

All these comparative reed behaviors seem bound up in ‘response’.  It’s asking a lot of one word.

When two people are engaged in a long and committed process of therapy, they work hard to find words and strategies to improve communication through effective dialogue. Maybe we need an equivalent effort to unpack that big umbrella word response?

To start, let’s consider response as a ‘physical’ dialogue between reed and bassoon. Based on the ideas suggested in previous chapters we can organize our thinking into two large categories.

Input + Output = Responsive dialogue

The reed starts the conversation.  Beginning with a brief stutter, the words fly – all of the available words.  The bassoon – initially unsure of the message – responds:

“Reed, too much information!  What are you trying to tell me?  Right now – with all these closed tone holes – I can only give you an F#.”

From the physicist’s viewpoint, the stutter is that initial engagement of the reed via the Bernoulli process with the bassoon, at first sending a complex jumble of frequencies down the bore, then the returning compression waves begin selecting for the most efficient frequencies.  The air flow starts the conversation – input (energy).

The bassoon answers with alternating compression/rarefaction – output (frequency).

On the one hand, input response describes the reaction of the reed to the flow of air from our lungs. On the other hand, output response describes the reed’s reaction to the pressure variations in the bassoon bore.  It’s a two-way process, the Yin and Yang of reed making.

The famous Taoist symbol suggests the interconnectedness and interdependence of opposites – approaching oneness thru duality.  We can use this concept to achieve a holistic way of thinking about designing bassoon reeds.

The mechanical reaction of the reed to the input of air is the more traditional way of characterizing reed ‘response’.  Observing the acoustic reaction to the output of internal pressures in the bore is the more complex way of defining response.  Successful reed making depends on both the mechanical reaction to the air you put into a reed AND to the reed’s phenomenally complex compliance with the pressure variations of the bore.

In future chapters I’ll flesh start out these deeply interconnected processes – the dialogue between input and output response.

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

Doodles etc by Nadina

 

thesaurus, bassoon reed response dialogue

talk to me

Brains and Membranes by Christopher Millard – Chapter 7 – Look Both Ways

Brains and Membranes by Christopher Millard – Chapter 7 – Look Both Ways

Brains and Membranes

Bassoon Reed Making

by Christopher Millard

Chapter 7 – Look Both Ways

Bernoulli Bassoon Reeds

Now, we’re going to review some of the ideas in the previous chapters. I find that changing the language just a bit often helps to illuminate understanding.

Daniel Bernoulli [1700 – 1782]

Heck of a guy.

Liife of the party.

Last week I showed you this little beauty: P + 1/2pv2 + pgh = constant

You still really don’t need to understand the math.  Remember that when air flows next to a surface and increases in velocity, the measurable pressure on the surface is reduced.  

Bernoulli’s idea helps explain a lot in life, from carburetors to naval architecture.

Consider the miracle of flight.  Much of the lift from an airplane wing can be explained by this principle. The shape of a wing will usually include a more curved upper surface and a flatter underside.   This means that air has to travel further on the upper surface of the wing then the lower surface, so it must travel faster.   Good old Bernoulli tells us that the resulting pressure on the upper surface of the wing will be less, leading to a good deal of lift.

 

Bernoulli Plane Reed

Blowing into the bassoon reed accelerates the flow of air, reduces the internal surface pressures and causes the blades to be drawn together.  It’s the first step in the process of converting air pressure into sustained bassoon tone.  Just as Bernoulli’s Principle helps us understand how an airplane gets off the ground, it also explains the process by which the reed begins its engagement with the bassoon.  You could say that the reduction of internal pressure, bringing the blades of the reed together, gives a constant ‘lift’ to the system and keeps the tone in flight.  Even on a bad day, that should lift your spirits.

 

 Bassoon reeds are a special class of acoustical pressure valves; they close in response to input flow [from the player] and open in response to output pressure [from the bassoon].  Bernoulli shows us how the blades come together when we blow.  Once closed there’s no longer a flow of air to suck the blades together.  At this point, the natural resiliency of the cane forces the blades open.  Once open, the airflow is readmitted, the air velocity increases, the internal pressure drops and the blades are drawn closed.  This process happens over and over and over, and we have sustained tone.

The frequency at which this constant reengagement of the air stream occurs is determined by the change of internal pressure inside the reed.  Remember: the reed sits at the apex of the conical bore of the bassoon, and its interior experiences constant variations in pressure as the sound waves within the bore oscillate back and forth.   The blades of the reed will be forced open when the internal pressure begins to increase, allowing airflow to resume and reinitialize the process.  The shift of internal pressure from minimal to maximal pressure occurs as the sound waves change direction, a process occurring at the frequency of the fundamental resonances of the bore.  If the player has chosen to play a low A, 110 times a second the pressure waves in the bore shift direction; 110 times a second the pressure at the apex of the bore [where the reed sits] alternates between rarefaction and compression.

That shift from low pressure to high pressure controls the timing of the reed valve opening.   So, at 110 Hz, repeated compression waves signal the reed to open 110 times a second.  Each time it opens, the influx of air from the player causes the valves to close and emit another pulse of energy.

Over and over, at the rate of the fundamental frequency of the note being played, the reed reengages the acoustical activity in the bore – and is at the same time controlled by it.  As a pressure controlled valve, its own operating frequencies are determined by the natural resonating frequencies for any given length of bassoon bore.

It is a two way street, a bidirectional process, and a complex interaction wherein the bassoon reed serves the acoustical needs of the bassoon.

Join me next week for a slight change of pace with Chapter 8 – Dialogue

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

Doodles etc by Nadina

 

look both ways

Brains and Membranes by Christopher Millard – Chapter 3 Surf’s Up!

Brains and Membranes by Christopher Millard – Chapter 3 Surf’s Up!

Brains and Membranes

Bassoon Reed Making

Chapter 3 -Surf’s Up!

by Christopher Millard

Surf’s Up!

A bassoon without a reed is like a violin without a bow.

Just as a bow serves as the energy conduit from bow arm to instrument, the reed converts the blowing energy of the bassoonist into the sustained acoustical energy within the bore of the bassoon. Sound in the bassoon is produced by the complex motion of compression waves within the bore of the instrument.

Sound pressure waves on a violin string act transversely; when you pluck a string it vibrates back and forth, while remaining fixed at both ends. We are used to seeing various kinds of transverse waves – at the beach on or two-dimensional diagrams.  When we watch ocean waves moving towards land we know that the water molecules themselves are not travelling very far; it is the travelling energy of the wave that we see moving forward. Water is essentially non-compressible, so the waves must assume peaks and troughs.

Because air is compressible, wind instruments function using longitudinal waves.

This is a bit hard to visualize, so here is a little thought experiment to help you understand.

 

Imagine taking a group of eager bassoonists and lining them up in a row – all facing one direction. Each puts their hands and the shoulders of the person in front, like a Conga line. Now, imagine that someone bumps the person at the back of the line and nudges them forward a bit. This would cause that person push into the guy in front of him, who would then push into the lady ahead of him, and the initial bump energy would transfer from that first bump all the way to the front of the line. This is how compression waves travel in an instrument, each molecule being pushed and itself pushing, until the initial input of energy comes out at the end of the bore.

Imagine a compression wave moving from the tip of the bocal to the end of the instrument. What happens when that energy meets the first open tone holes or the end of the bell? Fortunately, a great deal of the energy is reflected back into the bore. Thank goodness.

Imagine that you are all lined up as before, but this time the guy at the front of the line is standing at the cliff edge of the Grand Canyon. When the girl behind him pushes, he is going to yell really loud and try not to fall. He is going to try and resist the transition that occurs from the contained line of compressed people into the vast open space ahead of him. So, he screams and releases some of his energy. Then he leans back – relieved that he didn’t fall – and starts the whole pushing process in reverse.

This longitudinal back and forth is the way sound waves act in a bassoon.

The guy at the front of the line emits some energy when he screams, but he doesn’t quite make the big jump. In our conga line analogy, the first open tone holes are the cliff. Only a portion of the transferred energy escapes the first open tone holes, the reset start pushing in the opposite direction, all the way back to the reed where the first push started.

If wind instrument bores gave up all their energy to those first available openings, we would not have wind instruments. Let me repeat this in slightly different language: when the compression energy of the longitudinal wave meets the Grand Canyon of the open tone holes, most of that energy reverses direction and heads back to the reed, where the process will begin again. Compression waves are always followed by rarefaction waves, travelling back and forth in the instrument. Because this all occurs at the speed of sound, the alternation of direction happens many times a second.  The frequency of that directional alternation determines what we call pitch.

Violin strings have natural frequencies determined by their diameter, tension and length.  Bassoons have natural frequencies determined by the length, internal diameter and taper of the bore. Violinists control pitch by shortening strings with the fingers of their left hand. As bassoonists, we have control over pitch by modifying the length of the bore according to tone holes and keys we open and close. Longer bores produce longer wavelengths [more people in the conga line] and lower pitches. Shortening the bore produces shorter wavelengths and higher pitches.

This is pretty easy: in a violin, the tension of the four strings and the placement of the fingers determine the pitch In a bassoon, the length of the air column determines the note you play.

This is not so easy: just as a violin string operates with simultaneous modes – harmonics – so too does the bassoon.

We’ll get to that and much more next week!

 

If you want to learn 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

Doodles etc by Nadina