One of the most humbling and interesting things about crafting shakuhachi is that there’s no single one which can have it all. Each design choice and every shakuhachi will have its strengths and weaknesses. For instance, a shakuhachi made from a cylindrical pipe, like the silver Boehm, will have perfect tonal balance, the greatest ease of play, the most uniformity between notes, and the highest volume. However, it won’t respond well to breath-attacks which are integral to shakuhachi playing, it will have the least inherent character because of its uniformity, and it won’t produce an engaging feeling in the embouchure like traditional tapered “conical” bores (“back-pressure”).
The sculpted or casted human-made tapered bore of jiari shakuhachi seek to be more like cylindrical bores while bringing in a bit more character, good response to breath-attacks, and a more engaging feeling. Makers typically sculpt the bore of jiari to be narrower and smoother than what’s found naturally with Madake bamboo. This makes their sound more brassy, cutting, and clear. It also makes it possible to play more 3rd register notes, though these aren’t used in traditional shakuhachi music. However, narrow is narrow and they can feel comparatively restricting. Specifically, breadth of range in Otsu and Kan is diminished (the 1st and 2nd registers). For example, if we keep constricting the bore we’ll lose Otsu altogether, followed by Kan, and eventually we’ll have a dog whistle. Just like with any design choice, there are always pros and cons.
Conversely, wide bore shakuhachi will have more bass but Kan will be difficult compared to smaller bore shakuhachi. Kan will also sound comparatively weak and many players won’t be able to access it on the highest notes. As bores get wider we start losing notes in Kan, then in Otsu, and finally we’re left with just the hissing of our breath. Lastly, a medium bore shakuhachi will provide the greatest balance and range in Otsu and Kan, however, it will lack the punch and ease of a narrow bore and it won’t have the bass of a wide bore. Because of this, some people find medium bores to be “lukewarm” and unsatisfying.
Jinashi will tend to have so much inherent character that they’re dysfunctional by most people’s standards. It’s possible to bring some balance to them by adding or subtracting from the bore in key spots. It’s very rare that one will be naturally balanced and not require or benefit from this (at the moment, people call jinashi which have any additions to the bore jimori which is a word that wasn’t used when I started back in 2005).
Of course the bore is just one variable, though it’s such an important one. Everything about the blowing-edge and finger holes can skew things quite a bit. For example, one can make a narrow bore less brassy and more warm sounding by reducing the size of the finger-holes. One can begin to see how all of the attributes of shakuhachi are intertwined. As such, some attributes will be diminished or lost in the pursuit of others. In the end, all shakuhachi are balanced differently with their own strengths and weaknesses. Hopefully we can find what we need or enjoy. Ro on, Jon~