On Sat, 19 May 2018, at 21:34, RJ Skerry-Ryan wrote:
> It may not be the state of the art, but RubberBand
> <https://breakfastquay.com/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.

See here for a page very briefly summarising how Rubber Band works:
In short, it's a phase vocoder that uses a handful of the available tricks to 
try to reduce phasiness, without doing any very expensive analysis such as 
sinusoidal modelling.

There is actually a fine sinusoidal-modelling time stretcher hiding in 
Audacity, using the SBSMS library by Clayton Otey. This isn't a real-time 
method as far as I can see, and is slow to run, but it's worth checking out -- 
you activate it by selecting the Change Tempo or Change Pitch effect and 
checking the option labelled "Use high quality stretching". Code at 

Stephan Bernsee's old post is a bit of a puzzle, since it contains quite a lot 
about analysis/resynthesis but very little about actual pitch shifting.

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