Me again! I tried to experiment with iReal b and amplitube more today. But latency really turns out to be a problem, at least with my iPod touch 3G. With Amplitube running in the background, the guitar sound is just too late und messes up rhythm and timing. It does not really matter if I choose lateny "low" or "ultra low" in Amplitube, but the latter causes some clicking sounds in addition. Any ideas or recommendations - or is my iPod just too weak for the task?