SoundTouch is time domain, based on a Synchronous-OverLap-Add (SOLA). I
haven't gone through the source, but an article on their website explains a
few different methods and states at the bottom SoundTouch is SOLA based.

I've used SoundTouch a lot since it's one of Reaper's built-in algorithm
options, anecdotally I can say it works well enough on monophonic sources
like a voice but anything complex enough quickly turns into "glitch as an
effect" type of artefacts rather than remaining very useful for its
original purpose.

I think Elastique Pitch is the best among Reaper's built-in realtime
algorithms, it has "Soloist" (for monophonic) and "Pro" options too, but it
seems that one is proprietary...

On Sun, May 20, 2018 at 10:17 PM, robert bristow-johnson <> wrote:

> ---------------------------- Original Message ----------------------------
> Subject: Re: [music-dsp] Real-time pitch shifting?
> From: "RJ Skerry-Ryan" <>
> Date: Sat, May 19, 2018 4:34 pm
> To:
> --------------------------------------------------------------------------
> > It may not be the state of the art, but RubberBand
> > <> is, I believe, the best open
> source
> > pitch shift / time stretch library out there at the moment, and can run
> in
> > realtime on modern CPUs. SoundTouch <>
> is
> > another good option that is cheaper to compute (and therefore easier to
> run
> > in realtime on e.g. a mobile CPU).
> >
> these both sound interesting (in their demos).  thanks for filling me in
> on these.  the SoundTouch at stretch to double mode (or cut tempo in half)
> has splicing sounds or "glitches", many per second, so i sorta suspect that
> one to be time domain, but maybe it's not.  i wonder what that might sound
> like for monophonic vocal or something that might expose the "phasiness"
> that i dunno how to beat using a phase vocoder.  a good time-domain pitch
> shifter (not multiband pitch shifting) naturally is able to keep phases
> between harmonics synchronized (because it doesn't separate the harmonics
> and deal with each separately).  but there is the potential for glitches
> when the input is not sufficiently periodic.
> --
> r b-j               
> "Imagination is more important than knowledge."
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