A method for shifting a pitch of acoustic signals, which are expressed in terms
of a series of digital signals, to an optional pitch, uses a compacting and/or
expanding process on the time axis and cross-fades a fade-in acoustic signal, stored
in a memory with a fade-out acoustic signal, also stored in memory. The compaction
and/or expansion of the time axes minimizes phase differences between the fade-in
and fade-out acoustic signals to minimize tremolo in the output signal. The reduction
in phase difference employs fundamental tones of the two series of signals selected
by low-pass filtering the acoustic signal. One embodiment performs two-step compensation
with a rough compensation using blocks of the digital signals and a fine compensation
using samples from blocks.
