The impact of delaying local playback is especially evident in the case of digital music. In a non-networked scenario, where a user is merely playing a digital instrument, this delay is imperceptible. In a tele-orchestra, however, a software application modifies this delay depending on how it is operating within the teleconference. If the tele-orchestra's playout schedule demands that local playback be significantly delayed, then the user will notice the delay between when keys are pressed and when notes are played. The digital music scenario imposes other constraints on playback delay.
Humans can only tolerate a small actuation-instrumentation delay.
Informally, we have restricted ourselves to less than 300 milliseconds, and we have found that larger delays are almost universally intolerable. Small delays are quite tolerable. A person's reflexes automatically compensate, and the person presses keys slightly earlier in order to hear the notes played at the proper time. Rapid or frequent variations in this delay, however, impair the natural reflexes that enable humans to cope. If the actuation-instrumentation delay changes between notes, or every few notes, then the instrument becomes noticeably harder to play.