Low volume, timbre and latent power
The common practice is to take shakuhachi sound and work on expanding it with power and a strong tonal core. However, looking towards the other end of the sound arena, you can find enormous potential in the barely-heard tone.
Small sounds are not low-powered. Nothing gives the impression of authority so much as power which is hidden, merely hinted at. A lot of focus and power can be brought to small sounds, which still yield a small sound, but with a sense of held back, hidden energy. So when dynamic contrast is employed in a honkyoku phrase, the contrast is not between weak sound and strong sound, but is between hidden sound and exposed sound. Hidden sound can be practiced so as to be full of color, rich in timbre and powerfully restrained.
Pitch, power and the teacher
Spending time with your teacher gives you the opportunity to formulate and retain a model of sound that includes tone quality, pitch accuracy, power and musicality. The Japanese teaching system of playing with the student pulls skills out of the student as they try to emulate their teacher. These lesson experiences become the reference memory bubble that the student takes with them into their own practice at home. Yodo Kurahashi once said in a lesson to beginners, “If you only remember one thing from our lesson today, just remember the sound of my flute.”