On Thu, 25 May 2000, Eirikur Hallgrimsson wrote:
>
> Assuming that you can build hardware that somehow does discriminate
> pitch as fast as we do, you have the latency issue that you are now
> ready to start playing the note that the human audience has already
> heard from the source (whistle, guitar-string or whatever) and you
> start late. You just can't make this work in real time performance
> situations, even if you can hide the original control signal from the
> audience. The control signal matched the timing of the other
> performers, but the resulting tone is unavoidably late. Playing solo
> doesn't solve it either because what you are hearing is the note that
> you were humming, played as trumpets, not the one that you are trying
> to hum right now. The actual note-rate (tempo) that can be
> accomplished is really slow.
Audio-to-pitch *is* effectively a solved problem.
Latency is not an issue and the amount of DSP required to do this well
is dirt cheap. For example, there exist cheap boxes that will do
real-time pitch correction, a function which requires both detailed pitch
discrimination *and* artifact-free signal re-synthesis. One popular one,
the Antares Autotune, has a latency of <4ms, which is effectively
instantaneous in audio terms (esp for live use). In practice, solid
implementations of these pitch discrimination/resynthesis algorithms are
transparent and highly effective.
Fact is, the only parameter that needs to be manually adjusted on most of
these types of boxes is the amount and nature of nuance you would like to
keep in the signal (since most nuance is computationally indistinguishable
from poor pitch control). Setting these parameters to values that match
the style of play reasonably well will produce the intended results.
(Setting these boxes to absurd slew rates is a popular vocal effect these
days.)
-James Rogers
jamesr@best.com
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