Just trying to get a clearer understand so hope these aren't too noob-ish. If you have several processes wanting to send audio, does the callback go to all of them at (essentially) the same time, or does Jack poll them? If the former, is it the quickest to complete that gets processed first? If the latter, does Jack maintain the same order (assuming none stop) or might it change between buffers? I've a few more questions but they depend on whether either of these scenarios is correct! -- Will J Godfrey http://www.musically.me.uk Say you have a poem and I have a tune. Exchange them and we can both have a poem, a tune, and a song.