(A YouTube video in which I demonstrate TransposerRT can be found here. Please forgive the amateurish quality of the video; you'll hear background noise from my family, as well as pops and clicks from the freeware screencasting software I was struggling with. I'm much better at making M4L devices than YouTube videos, I promise!) Have you ever wished that you could play notes on one MIDI track, and have those notes be applied as pitch transpositions to what's playing on other MIDI tracks? Well, now you can. TransposerRT is a freely downloadable pair of Max For Live MIDI Effect devices -a Sender and a Receiver- which together make Ableton Live much more flexible for improvisation, allowing you to send pitch transpositions to multiple MIDI tracks simultaneously on the fly. For example, say you have a bass track and a string pad track each playing their own clip, while you improvise the melody on another track.
External for hosting Apple's AUTimePitch.