Even when you are good at the shakuhachi, sometimes you have trouble getting the right tone. For instance, notes may have a tendency to bleed into the upper octave.
One cause for this is too narrow of a vertical passageway for the air to pass through. I’ve discussed this before, so now I will discuss a different factor: The point the shakuhachi rests on your chin.
When the shakuhachi isn’t resting on your chin in the exact right location, it can have a deleterious effect on your playing. It is rare for the shakuhachi to shift horizontally, but it happens frequently that the shakuhachi will slipeither up or down on the chin. Even slipping up or down by 1 mm can cause your notes to jump into the higher octave by accident.
All that is required to fix the problem is to move the shakuhachi back to its proper position. Often, however, it will slip back almost immediately,sometimes without your noticing. The only way to fix the problem permanently is to change the balance in the way you hold the flute.
The flute is balanced between three points: your thumb and middle finger in your lower hand and your chin. Your chin pushes gently against the flute, pushing it forward, while the thumb and middle finger of your bottom hand
push it gently back into your body.
The relaxed balance between these two forces is what keeps your flute in position.In order to permanently fix position of the shakuhachi on your chin, you have to adjust this balance.
The way to subtly change this balance is to alter the position of your thumb of your bottom hand. Slide the thumb slightly upwards along the flute to weaken the backwards force, or slide it down the flute to strengthen the backward force. This will allow you to precisely determine the position of the flute onyour chin without worrying about it slipping.
The position of your bottom thumb may be a subtle factor effecting your sound.Experiment to find out.