Mujitsu and Tairaku's Shakuhachi BBQ

One scientific explanation of the difference between tapered (conical) and cylindrical bores is that each causes a difference in the resonant modes, and hence the overtones which can be excited.

In practice, a tapered shakuhachi bore can give the timbre more depth and greater blowing resistance - features which many players find desirable. It is also one way of improving octave tuning.

A cylindrical bore can give a shakuhachi a quick attack and perhaps for some tastes, less mystery.

These are personal observations, but perhaps shed some light on why (for shakuhachi) a tapered bore is usually the norm.

As always, there are many ways to look at this. (Opening can of worms!)

Ken

- Another thought: The tapered bore of modern shakuhachi closely mimics much of the natural bore of rootend cut bamboo. Hmm, which came first?

Toby wrote:

My personal experience with quena flutes, most of which are reverse conical but some of which are cylindrical, gives me the impression that the reverse taper has important consequences in the or third register of the quena, which corresponds to the dai-kan in the shakuhachi. There is some very complicated business with tonehole lattice effects, which I believe make it easier to produce very high notes using a reverse taper.

Toby

I just want to make sure I'm following this conversation correctly. Is reverse conical the same thing as reverse taper? You're using two different terms that I think you are using to mean the same thing, but I'm not sure.

Toby wrote:

No clarinet has a reverse taper, although Buffet pioneered the "polycylindrical" bore, which is slightly wider at the top. Essentially a reverse taper is acoustically equivalent to a cylinder, but it slightly flattens the lower resonances of the tube in an interesting way. A commentary on the reverse taper (from "The Physics of Musical Instruments", by Fletcher and Rossing) is as follows:

"We might speculate that one of the advantages this form of impedance curve [sorry, the explanation is too technical to include-Toby] confers on a tapered instrument relative to a cylindrical one is an increased pitch stability with blowing pressure, for the asymmetrical shape of the lower resonances tends to reduce the drop of pitch as the blowing pressure is lowered, while a rising pitch at high blowing pressure is self-limiting ...however the effect is very small."

My personal experience with quena flutes, most of which are reverse conical but some of which are cylindrical, gives me the impression that the reverse taper has important consequences in the or third register of the quena, which corresponds to the dai-kan in the shakuhachi. There is some very complicated business with tonehole lattice effects, which I believe make it easier to produce very high notes using a reverse taper.

Toby

That makes sense... as a side note, the book sounds fascinating as well. Thank you.

Mujitsu wrote:

- Another thought: The tapered bore of modern shakuhachi closely mimics much of the natural bore of rootend cut bamboo. Hmm, which came first?

Knowing the Japanese, they probably based it on the natural bore with less regard for the resulting sound... I wonder what they would sound like if they flared at the end. Are there any shakuhachi out there which do that?

Flaring the end will raise the pitch of Ro but it seriously changes the tone of the flute.
Better i think to re-calculate so Ro does not need to be raised this way, then you have the greater option of tone dardness or brightness.
It may also influence the 'honk' of the flute, though I have not fully understood what causes this yet.

Kel.

Toby: if you google "clarinet" "reverse conical" and simply read the descriptions of various clarinets in the summaries that come up, you'll see reverse tapered bore instruments such as the Paris etc. Whether these are truly evenly conical or polycylindrical plus a Moennig or Chadah barrel, I don't know, but they're advertised as reverse conical at least. Various clarinet forums also talk about reverse conical instruments. It could very well be that the combination of a Moennig barrel plus a reverse-conical upper joint qualifies a clarinet as "reverse conical," I don't know. A good general article on the acoustics of all this is http://www.sfoxclarinets.com/baclac_art.htm , which also differentiates between reverse conical and polycylindrical. I would imagine if a clarinet is TOO far from cylindrical it would overblow an octave rather than a 12th... but I am definitely no clarinet expert, I only know a little from talking to people I play with (I have often fantasized being a clarinet player!)

Alan Adler wrote:

Toby wrote:

My personal experience with quena flutes, most of which are reverse conical but some of which are cylindrical, gives me the impression that the reverse taper has important consequences in the or third register of the quena, which corresponds to the dai-kan in the shakuhachi. There is some very complicated business with tonehole lattice effects, which I believe make it easier to produce very high notes using a reverse taper.

Toby

Hi Toby,

As usual, your posts are quite interesting.  Can you supply some dimensions on the quena flutes.  Bore at top, at bottom, length, hole diameter.

Best regards,

Alan

Hi Alan,

When I am back in Tokyo next week I will send some measurements.

Hi Nyokai,

I checked the link you provided from Stephen Fox. If you read closely you will see that when he talks about "reverse-conical" it is always in reference to bore of the clarinet barrel. Look at the graph of the French bore and you will see that except at the very top and at the end, the bore is totally cylindrical. I suppose one could argue that any point of reverse taper would count as a reverse-conical bore, but personally I would use the term "reverse conical bore" for an instrument in which the bore tapers more or less smoothly for most of the bore under the finger holes until (at least) some point near the end. It is interesting to note that the shakuhachi is the only reverse-conical bore instrument that I know of that flares back out again near the end, like the clarinet. Old-style flutes and recorders continue the reverse taper to the very end of the instrument.

BTW as the cone angle is progressively reduced the mode frequencies are correspondingly widened, until the limit is reached at the cylinder in which the 12th is sounded as the first partial. If you start widening the clarinet from a cylinder it will overblow an 11th, a 10th, a 9th, etc. smoothly, until at a certain cone angle it hits the 8th--the octave--and effectively becomes a saxophone!

Toby

Last edited by Toby (2009-09-29 05:29:05)

Here is one more point of clarification on my last post. Theoretically any complete cone will overblow the octave, no matter what the cone angle. This all changes when you cut off the end to have a place to put a mouthpiece. That will throw off the mode resonances (and thus how the higher modes relate to the first) to an extent depending on the both the truncation ratio (amount of the cone cut off in relation to the total length of the cone) and the cone angle. You  might notice that the truncation ratio changes as you open more keys, so different notes will overblow different intervals.

Restoring the resonances to the ideal--or close to it (so that it overblows an octave)--depend on making the mouthpiece of the right dimensions to mimic the truncated conic apex. There are a couple of ways to do this, but I won't go into it since this is a flute forum.


Alan--I haven't forgotten about the quena measurements. I'm back to Tokyo in about a week but quite busy filming for a documentary for several weeks after that. Hopefully I can get you some info around the middle of December.


Toby

Last edited by Toby (2009-11-17 06:55:46)