Also, from the API, it seems that I could implement Paulstretch algorithm ( http://hypermammut.sourceforge.net/paulstretch/ ) easily. When I'll have some free time, I'll try it. EDIT: I looked a bit closer on interface EFFECT and Paulstretch cannot be implemented as an effect, but as a generator. Needs to be studied more :)
Paulstretch would be a perfect addition to the library, it would open whole new doors for example for samplers (whoa, the sample is sustained forever!), of course with some limitations in regards of real time. Send me a message on GitHub, if you decide to take up on the task, I'd be glad to give you a hand with it! :)
If you want to look at the algorithm of Paulstretch you can have a look to a simple Python implementation: https://github.com/paulnasca/paulstretch_python/blob/master/... The algorithm is pretty fast, the most time consuming operations are the FFTs and IFFTs. That's why I think that it might work on real-time JS.