Performer

Are you an Ableton Live user that wants to play multiple MIDI controllers during the performance, but you cannot combine the live performance and the MIDI tracks playing the recorded clips?

Performer is an Ableton M4L device that enables you to do it!

Create a new MIDI track, drop the Performer.amxd to it, set its Monitor to "In" and choose the MIDI controller from the "MIDI From" drop list.
Then choose that new MIDI track as the "MIDI From" source for the track that you want to control. When you start playing on your MIDI controller, controlled track's Monitor will switch from "Auto" to "In" automatically, which will temporary mute the playing clips, and let your performance be heard. When you stop playing, after the configurable release timeout (3 seconds by default) the track will switch back to "Auto" and playing clips will unmute.

Set up as many controllers as you like and make your performance intuitive and convenient!