The four components of music
Music has four main distinguishable aspects:
-Rhythm
-Pitch
-Tone color
-Dynamic shaping
Of these, the first two are non-negotiable. Without correct pitch and correct rhythm, music loses its basic skeletal structure and becomes less intelligible or completely unintelligible.
The second two aspects, timbre and dynamic shaping are the muscles and flesh of the music, and bring the musical form into clarity and nuanced performance.
Perfect playing
So, what can be called perfect playing? Students of shakuhachi struggle for a long time with basic sound production. The early days, with simple folk songs, for example, are concerned with making a sound, following the notated timing and getting some control over pitch and pitch intervals. The business of timbre and dynamics tends to show up later in the learning process, (with the exception of meri).
The shaping and character of meri notes as 'yin' sounds should be the player's first awareness of timbre and dynamics in all Japanese classical shakuhachi music, and this is as important to 'perfect playing' as pitch and rhythm, even for complete beginners.
To be able to play a simple piece with good pitch and good timing and attention to the soft yin qualities of meri is quite an achievement in shakuhachi, and thus I call it 'perfect playing'. Those three parameters will make Japanese classical music comprehensible, irrespective of any other nuances of timbre and dynamics.
Kurokami
The classical piece, Kurokami, is considered in the pedagogy to be a 'beginner' piece. It takes a lot of work to consistently play Kurokami all the way through without any mistakes, with good pitch and correct timing and respect for meri quality.
When you can do that, I call it 'perfect playing'.
At that point, the player can begin to direct focused attention as to how the timbre can change, dynamic contrast, how pitches are modulated and flow from one fingering to another, the emotive content of the sung poem and the partnering ensemble shamisen part. These aspects are always in play, but until the player has a good control of pitch and rhythm and meri, they tend to take a back seat.
If you are studying a simple folk song for example, aim to be able to consistently play it 'perfectly'. Keep playing until you dissolve all the mistakes in the timing and pitches of the piece. That is the beginning of the music.
The Theatre of Phrasing
The music unfolds in your hands as a series of interconnected phrases, which combine to make motifs, which in turn combine to create the larger rhythms within the composition. Ultimately, it can all be perceived as a one-ness, a complete self-contained musical experience.
All fingered notes are equally important and each phrase needs the deepest attention possible, in every microsecond of its unfolding, to find the fullest expression of the intended musical theatre.
A simpler way of explaining this is: always give everything you have, every time, to every part of the music, no matter how tiny.