FFTs and retuning

JdL wrote:

>Bill, this is too kyool!! Do you mean to say you could retune, say,
>one of Jay's tracks of Christmas music? How much CPU does that take?

Sorry if I left the wrong impression.
I doubt that retuning a full composition from a sound file is possible,
if by this one means transposing each "voice" in an independent
way. My stuff, (along with everyone else doing retuning) only works
effectively on monophonic timbres/sounds/instruments. So, if one had
a kind of master tape in which each voice was on a different track,
then yes, it would likely be do-able, but if the voices are already
mixed down to stereo, then probably no.

I was replying to your question about the technique of
transforming a sound with an FFT, and then mapping the partials
(which is one way of doing pitch shift), and then transforming
back into a sound.
My interest in the technique (and the focus of the
CMJ paper), was to move the partials around so that they became
more consonant with a set of desired scale intervals - for instance,
suppose you wanted to work in 10-tet. The nearest thing to a fifth
is at 720 cents, which tends to sound very out-of-tune
when used with harmonic timbres. But if you move some of
the partials around (for instance, move the third harmonic
to near 720 cents, instead of near 700 cents), then the
roughness is greatly attenuated. But the technique also is good for
straight pitch transposition (over short intervals, like all
pitch changing techniques).

>>the article also has a CD so you can hear some of the possible
>>effects and side effects...

>Where can one get this CD?

It was distributed with the last issue of 1998 CMJ
(their CDs come out once a year, "illustrating" the articles
from that year.) Alternatively, there is quite similar stuff on
the CD that comes with my book, Tuning Timbre Spectrum Scale.
(the sound examples illustrating the spectral mappings chapter).

Bill Sethares

William Sethares wrote:

> I doubt that retuning a full composition from a sound file is possible,
> if by this one means transposing each "voice" in an independent
> way.

What about with Kelly Fitz' LemurPro for Mac? Still a load of work (and for
me, a lot of waiting) but it would be _possible_ to retune instruments or
their partials in a polyphonic file.

Clark