How the Shakuhachi is actually used as a meditation practice (suizen 吹禅,
"blowing Zen") is a topic often overlooked and seldom referred to
explicitly. I have selected some of the teachings that I have received
over the years from my teachers. Those hints might help you to get
started if you already are a Shakuhachi player.
1) Play regularly.
Needless to say that you need to play as much as you
can. "I'm not in the mood today" etc. is a silly excuse, Shakuhachi can
be played in any mood, that's the point.
2) Play by heart.
You need to memorize some pieces to be able to practice suizen. Start with short ones. Shakuhachi is about experiencing sound, not about looking at scores.
3) Play freely.
Don't get caught in the form of a piece too much. Play the way you remember it and check afterwards where you need to revise.
4) Halt and watch.
From time to time you should stop in the midway of a piece and listen/watch the quality of the silence (shikan止観).
Some pieces have little hints in the notation where to stop, most
don't. After playing for a while your breath will change and so will
your ability to watch your mind.
5) Finish your practice without finishing your piece.
When you finish your practice session always stop in
the midway of a piece. The unfinished piece will resonate through your
day and your everyday life will naturally become part of your
meditation.