Any help is welcome.

Hi, Nuno!

FFT is certainly a option but I think I'd start by trying LiSa. LiSa (LIve SAmpling) is a new Ugen that's not in the manual yet but is documented in /examples/special/ in your ChucK dir. She (LiSa is a female Ugen, I feel) is quite capable of granulating and I think one of the examples there covers this. If there isn't one for some unforseen reason we need one, I think.

Any time-streching or pitch-shifting will create artefacts so the trick is picking one that suits your material and perhaps fine-tuning it but generally speaking LiSa can do this kind of thing if provided with a bit of frame-work.

Hope that gets you started. If push comes to shove we could try using FFT to detect the most prominent frequency in the source material and use that to set the grain length and/or rate, that might be a interesting strategy if you'd run into artefacts and this is suitable for the material.

Yours,
Kas.