[music-dsp] Pitch Shifting

[robert bristow-johnson]

on 12/26/2004 09:34, Jürgen Schumacher at solastudio at gmx.de wrote:

> Concering real pitch shifting, you'll never gain a natural voice even if you
> try to maintain the formants: human vocal expression for upper tones differ
> from those for lower tones significantly so there had to be a format
> shaping/modelling instead of a format maintainance.

i dunno how "natural" you need it, but there are both frequency-domain and
time-domain techniques of pitch shifting that preserves formants (or
attempts to).  probably the conceptually simplest to point to is what i
would call "Lent's algorithm" which is published in a 1989 Computer Music
Journal.  i'm pretty sure that the early Vocalist boxes and these Roland
Voice Transformers used that method sans Lent's pitch detection, which was
pretty poor.

pitch shifting that is not formant-corrected can be thought of as a
combination of time-scaling (the hard part that might introduce artifacts)
and resampling (mathematically straight forward).

-- 

r b-j                  rbj at audioimagination.com

"Imagination is more important than knowledge."