As Goldie climbs the ladders into the high register she finds herself thinking about the physical changes required in ascending passages.  The sense of moving air more quickly is vital to good sound production in the upper octave of the bassoon.  This is partly an aesthetic obligation – a crescendo in a rising phrase is a key musical instinct.  For instruments like flutes, an increase in dynamic comes naturally in upper registers.  But in the bassoon, volume and sonority tend to weaken in the third octave.  Let’s examine why.

Unless our reeds are too sharp [Baby Bear!] and stuffy, we typically get a lot of sound in the lower register. Most reeds with adequate flexibility produce more sonority at the lower end and less at the top. The bassoon is really 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; they have a big advantage in the upper octaves.

Goldie’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 – although that is frequently appropriate. Rather, the habit of adding more support in an ascending passage is a strategy to correct the register imbalance in bassoons: loud and edgy at the bottom and squeezed at the top.

Chapter 13 touched on the acoustical reasons for this diminishing upper register richness.  As we move to higher bore resonances the slight closure of the reed not only reduces the MCA value but changes how the blades respond to the Bernoulli effect.

Remember, each jump to a higher register reduces or eliminates a strong lower  harmonic.  Sonority suffers as fingerings and embouchure select for the higher frequency resonances, reducing the net energy of these remaining harmonics. Even the lightest reed and the most modest lip pressure dampens the membranes and adds resistance. Tenor register pitches in particular become less responsive to nuance and articulation. These changes in the reed/bassoon dialogue that encourage the upper register also conspire to reduce complexity and projection!

What’s our best tactic? 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.

The balance between air support and embouchure can be minefields in the pedagogy of both playing and reed making. We aspire to play in the third octave by moving the air faster and minimizing embouchure effort, but we sometimes expects too much. Most reeds also require a bit of help from the lips.

Chapter 10 saw our little bassoon character inside a huge, imaginary reed. Let’s climb back inside.

Observe in slow motion the blades flexing. You’ll see changes in the contours of the blades as the player moves from low register to high register. In addition to a more closed aperture opening you’ll see a reduction in the flapping motions in the wings. This concave collapse of the wings results from increased embouchure pressure, which act on the wider, thinner areas of the membranes. When blades are held a bit tighter, larger motions are restricted.  This dampens the lower harmonics and moves the reed into a Mama Bear or even Baby Bear dimension.

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.

Why does increased air pressure have so much effect on pitch?

This is a very confusing phenomenon, because in other instruments excessive volume tends to flatten pitch. We see this effect in the clarinet when it’s overblown. However, the bassoon will usually sharpen with increased air flow. Careful observation of vibrato production reveals that the acceleration of air several times a second not only causes repetitive increases in volume but also in pitch.  Increased air flow into a bassoon reed sharpens the upper bore resonances at an exaggerated rate.  In fact, the effects of embouchure and air on intonation increase exponentially as we move into higher bore resonances. That’s why vibrato is so hard to master up high, and why pitch bending in the high register can be so extreme.

The physics are a bit complex, but it seems that increased air velocity through the aperture both raises the natural frequencies of the membrane ‘shell’ as well causing greater inward displacement of the blades and decrease that theoretical missing conical aperture.  There are clear physical reasons why air speed sustains both register and pitch. The evidence is with us constantly.

Chapter 15 Resonance. It may not be what you think…

Chapter 1 – Starting Down The Path  Chapter 2 – It’s A Simple Question? 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 MyLipsChapter 15 – Resonance Chapter 16 – Corvids & Cacks Chapter 17 –   Chickens and Eggs Chapter 18 – Chiaroscuro  Chapter 19 – Donuts​ Chapter 20 – Balance

Doodles & Design by Nadina

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