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. 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 gazes back down the dark tube of the reed into the blackness of the bocal and feels the waves of pressure wash over her.
From the enormous aperture, our brave little physicist/bassoonist feels a gentle breeze blowing. 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 this shell, she watches the blade membranes undulate; they are interacting with both the air flow from the player and the complex multi modal pressure waves coming from the bassoon bore behind her. The sound is getting louder and with increased blowing pressure comes an increase in the vigour of the blades’ (membrane) contortions.
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 membrane activity 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; with increasing air input the blades are thrown ever closer towards each other, the aperture slamming open and shut like a screen door in a wind storm..
The milliseconds tick on. Repetitive patterns begin to emerge in the membrane behaviour, the complex irregularities are 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.
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!!!
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 up, Chapter 11 – A useful equation
i’m having trouble sleeping now