Brains and Membranes
Bassoon Reed Making by Christopher Millard
Chapter 20 – DONUTS – Part 2
Our Little Bassoonist is trying to make sense of this language about geometry and radial transitions. To see how her reeds evolve from tube to tip, she imagines sawing her reeds into numerous cross sections. She finds ever enlarging diameters as well as transitions from strongly convex at the back to flexibly concave towards the front.
What truly grabs her attention is the increasing complexity in the curvature of her blades. As the radius expands there is a gradual shift from convex to concave resting states!! This is a feature of all bassoon reed topologies. Whether big or small, wide or narrow, almost every reed has a region where expanding curvature interacts with ‘profiler induced’ softer cane to produce inward flexing towards the wings.
Whether or not you see obvious concavity at the aperture will largely depend on your reed’s width and profile – and ultimately your embouchure and air preferences. Our Little Bassoonist likes a reasonably wide shape, so her cross sections start to show a transition from convex to concave around the middle of her blades. More narrow shapes may not necessarily show concave collapse in the wings in their resting state. But even in a narrow reed, the wider portions of that reed must still flex inwards as the membranes respond to air flow. Inward flexing in the wings and sides is an inevitable outcome of the Bernoulli effect, where accelerating air flow reduces pressure on the inside surface of the blades. This induces closure of the blades, enhanced by the widening, arrowhead shape of the bassoon reed combined with typically softer profiles towards the wings. .
In Chapter 10 of Brains and Membranes, we shrank LB down into a tiny, time-dilated observer. She was able to witness the messy and non-linear oscillations of reed membranes. Nothing was very smooth! No sine waves, but instead lots of flapping and asymmetrical contortions. It’s chaotic. And yet, most bassoonists are persuaded that symmetrically balanced profiles and trims lead to better reeds. Is this a paradox? Do geometrically beautiful membranes – with smooth radial transitions – offer the best mechanism for harnessing the acoustical chaos and delivering better reeds?
This is a contentious subject for reed makers! Everyone has experienced reeds that appear unbalanced and irregular – yet somehow perform well. But, notwithstanding the fact that visually irregular reeds are occasionally fine, I remain convinced that highly symmetric reeds significantly improve one’s odds of successful outcomes.
Our Little Bassoonist [who has been forced to participate in these 20 arcane chapters about reed acoustics…] is coming to a simpler interpretation of all this: visualizing radial/topological transitions is just a search for functional balance. Many bassoonists associate ‘balance’ purely with dial indicator measurements, leading to matched profile thickness in all four quadrants. But functional balance is only revealed after the reed is built, when all the growth memories meet the newly imposed tube structures, revealing shape variability as the cane asserts itself in its new form.
Careful measurements with a dial indicator can be useful, but the structural inconsistencies of Arundo donax will more often bring disappointment.
The word ‘balance’ gets thrown around so much it might be wise for reed makers to consider better definitions. I think the word can describe the organized integration of axial and radial forces within the finished reed.
We all learn reed making through trial and error; remove a little cane and see what happens. If it works, we repeat the same maneuver on a similar reed and hope for a successful outcome. Younger players correctly follow their teachers’ suggestions, and despite inevitable disasters everyone eventually develops some reliable skills. But it’s mostly empirical. I’m not sure that we think through what happens physically to the reed behaviour when we take a knife or file to a particular spot. For example, will removing cane increase or decrease the potential for flexibility in any given spot? Will the removal contribute to overall radial symmetry?
All the past chapters of this blog are leading to a more holistic view of the reed valve and its complex Yin/Yang behaviour. My advice is to always follow this underlying principle: pay attention to structural symmetry. Well-planned profiles will give your reeds the best opportunity to demonstrate compliance with the non-linear, non-sinusoidal and acoustically asymmetrical internal standing waves.
LB is so often frustrated. Though she takes particular care with both her profiling and her blank assembly, her finished reeds are often irregular and warped. Great care, good intent, but puzzling asymmetry. Why? Part of the answer may lie in improving her assembly techniques, paying attention to the distribution of cane as pliers and mandrel interact. Everyone has a slightly different solution to getting the best possible blank. But there remains an overlooked practice that I’ve seen time and again – it’s over-reliance on profiling machines to do most of the work.
Asymmetrical outcomes typically result from overly profiled cane.
Throughout this blog I’ve avoided giving specific advice on techniques and designs. But I’m going to bend that rule a bit and suggest a protocol that I think will improve outcomes for many players.
I think most young players expect profiles to deliver 95% of their expected final trims. Of course, why not? It’s logical to use machines to do the work!
The most obvious weakness of that strategy is when a piece of cane is too weak for a given profile. You all know what it’s like to have 10 pieces of GSP and discover half of them wind up to thin and soft. But I’m addressing a more fundamental problem: profiles are so often not thick enough to maintain smooth radial transitions. When profiles are too thin, the brutal process of folding, applying wires and molding cane to mandrel easily lead to structural irregularities. These include precipitous radial collapse in the back sides, sudden transitions at the border between convexity and concavity in the wings, or simple warping in the front of the blades where the profile is thin. These all create unintended internal radial memories, where the four quadrant behaviours are too irregular for most efficient interaction with the acoustical turmoil going on inside. And the outcome of these unintended geometry changes? Compromises in resistance, control, pitch and tone color.
I want to suggest a strategy which I have employed for decades in my own reed making. Plan for two different profiles.
- The initial profile should be about 20% thicker than anything you might have used before! It’s a strategy that allows the blank to survive the rigorous forming process with better radial integrity.
- The second will be a ‘maturation’ profile that you impose immediately on the finished blank before it has time to dry and set up new memory.
LITTLE BASSOONIST ASKS: “I’M AFRAID TO TOUCH MY PROFILER. HOW DO I GO ABOUT THICKENING MY INITIAL PROFILES WITHOUT THE NIGHTMARE OF ADDING SHIMS, fooling with ADJUSTING KNOBS, OR FIDDLING WITH A BLADE THAT TOOK WEEKS TO GET RIGHT????”
Changing the initial profile is not rocket science. All profiling machines use a roller bearing on a carriage guide. Simply add strips of thick adhesive tape the full length of the guide to raise the cutting assembly and thicken the profile. You can use masking tape – start with 3 or 4 layers, or duct tape – 1 or 2 layers. A longer lasting solution is glue a strip of thick teflon using contact cement or a thick cyanoacrylate glue.
Of course, a better solution is to dive in and adjust the cutting depth of your machine. If you are sharing a profiler in a school environment, make sure to take clear notes of what adjustments you have made and then return the machine to its initial configuration.
The very best, absolutely most valuable solution of all? Hand profiling!! That deserves a full chapter by itself…
But what on earth is a ‘maturation’ profile?
It’s all about setting up your blanks to undergo the drying and aging process in a way that establishes ideal radial structure in the wings. Just like the laminated furniture, you want to take advantage of the new radial resilience that is imprinted in Arundo donax during the blank formation process.
There are two distinct approaches.
– If your reed making practices involve building a blank and letting it dry/age before cutting the tip, you should expect that the ‘topology’ that you see in the wings will be reinforced in the radial memory of the cane. That usually means that there will be a kind of neutral aperture in the wings when you finally cut the tip – neither strongly convex nor strongly concave. You will be accustomed to dealing with this aperture shape and it may or may not be serving your ideal tonal and embouchure needs. The downside to this approach is that a strong irregularity in one quadrant will still assert itself, and you will have to correct this when trimming.
– If your practices involve building a blank and immediately cutting the tip you will be able to make an instant assessment – both visually and with physical flexing – of both the symmetry and the concavity of your wings. Any imbalance that you leave at this point will be imprinted to some extent and you will have to correct this in the trim. However, if you make immediate corrections before placing the blank on the drying board, you will create an immediate imprint for symmetry during the initial rest – whether it’s a day or a month. Ultimately, this second approach is likely to give your reeds the desired shape with less cane removed from start to finish.
Great bassoon reeds are most likely to emerge when we respect the irregularities of organic material. Adjustments to your reed making that increase mass and density in the early stages will bear fruit in the long run. Less wasted time at the reed desk?
Certainly more time for donuts and coffee..
Text by Christopher Millard
Drawings by Nadina
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 Chapter 18 – Chickens and Eggs Chapter 19 – Chiaroscuro Chapter 20 – Donuts Part One Chapter 20 – Donuts Part Two Illustrations by Nadina