Constantly updating buffer with variable speed playback

Hello,

I'm a little stumped about the best way to accomplish this task. I want to record continuously into a buffer, and then (after a delay), play back the audio at different speeds.

In musical terms:

I want to set up a variant of what is called a prolation (or mensuration) canon (https://en.wikipedia.org/wiki/Prolation_canon). Let's say I have audio coming in from a voice, and halfway through the piece the buffer begins to play back the audio from the beginning of the piece at double speed, so that the continuously sampled audio comes close to catching up with the live performer at the end of the piece. (It's actually a little more complicated than that, but that's the basic idea.) There is no looping involved.

I checked out Andrew Benson's patch described here: https://cycling74.com/forums/endless-resampling, but it uses index~ and there are too many artifacts when played back at different speeds. Maybe I'm doing something wrong, but groove~ and play~ don't seem to work well with the continuously updated buffer as set up in this patch. Any ideas?

Thanks,

David