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.
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.
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…
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
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