Nearly everything about a shakuhachi affects the sound and feeling of it. From the volume or size of the bore, to the size of the finger-holes, and the depth of the edge or utaguchi. Mere millimeters of change can have noticeable or even profound effects. If a maker crafts a nobé or “whole” jinashi shakuhachi and leaves the inside mostly natural then nature determines more of the sound and feel. By contrast, a jiari maker fully shapes the inside using paste or glues and adjusts the length via a center joint. With jiari the maker decides most or more of the sound and feeling.
However, what often matters most is how much air or effort a shakuhachi takes and how that matches up with how much air or effort a player likes to use, or is capable of. What determines this is mostly the size of the bore or inner volume of a shakuhachi in relation to the total length, i.e., a ratio of length to width. More volume or a “wider bore” shakuahchi will accept/require more air or effort. Conversely, more narrow shakuhachi will take less air and require less effort. Wider shakuhachi can feel expansive to a powerful player while narrow shakuhachi can feel limiting. For a player with less power, however, wide shakuhachi can feel impossibly difficult while narrow shakuhachi can feel “just right”.