FYI, your app is currently being talked about on HN: http://news.ycombinator.com/item?id=1163268

One question I have:
Are you using feedback cancellation at all? For example, if you were to record while tracks were playing out of the main iPhone speaker, does that feedback get into the recorded track?

Hi Sofal !

Thanks a lot for the link, love tracking the discussions about the app .

There is no feedback cancellation, that's why you have the choice of outputting sound through the receiver (much far away from the mic, but less loud) or the speaker in the options.

I have some ideas to do feedback cancellation, but it's a really CPU heavy thing and I have to be careful with this. It'll require lot of testing without being sure that it'll be feasible in the end, so I'll not concentrate on that in the first place.

Thanks for your interest anyway Sofal !