Take ni awasete fuku

Depending on the character of the flute, the player needs to accommodate his or her playing style, even embouchure in order to play it. (Japanese expressed this pedagogical idea by saying take ni awasete fuku, or “blowing according to the character of each piece of bamboo”).

Shimura Satoshi uses the term “Iki no michi” (“route of breath air”). He claims that the ji-nashi shakuhachi, especially old ones made during the Edo period, shows a wide variety of differences. These flutes do not sound resonant unless the player accustoms himself to its character brought by its unique, innate bore shape. The player needs to change his blowing style in the way that the air passes through a uniquely shaped inner space of the bamboo. This process requires months of practice and acclimation. (In the interview posted earlier, he described that he had come across ji-nashi that didn’t sound well initially but later changed his impression).

Toya Denko (1984) goes so far as to say that the air carves bamboo:

The ji-nashi shakuhachi is different from one another in terms of inner bore space. The player needs to get used to its own blowing style. Otherwise, the pitch may be inaccurate and the sounding may not be rich. However, as he plays it for some time, he understands the tips of how to blow into it. Because it does not bear a filling material inside the bore, the bamboo fabric may naturally be shaped in time [by blowing air] in a way that it resonates well. This transformation is called “road takes shape” (michi ga tsuku).

How long does it take to shave the bore until the bamboo sounds good? Must be more than a couple of months. Not my experience.