From the program notes of Pien, composed in 1966. [continued]
Only 6 gradations are used. Consequently very sharp contrast (loudness discrepancy) must be achieved between the adjacent grades. The result should be of a terraced character (except in cases of crescendo and diminuendo, naturally):
ppp is used only in the percussion parts to indicate an imperceptible start of a crescendo.
|very heavy accent|
|heavy but short (secco)|
|sharp accent (regular)|
|very dry staccato|
|tenuto-attack with weight but not accent|
|slur:||very legato — noticeable portamento preferred|
should be executed evenly with subtlety and restraint, and strictly within a semitone.
Except for legato phrases, where the use of vibrato is at the player’s discretion, and wherever a slow and wide vibrato is indicated, the tone quality should always be as “thin” and “cutting” as possible, i.e., avoid the usual blend of “rich” and “diffused” quality.