Indeed, this is not very rev2-specific, but that's no problem. Is the following clear to you? (I see Maxter also just wrote an answer, at a slightly different level, so I post my answer as well)
If you record sound, you only have the sound to play back.
If you record midi, you only have midi to play back.
If you record both, you have both to play back.
If you have recorded midi, you can play it back, sending it to your rev2, which will then make sound according to the notes in the midi recording. You could record this sound. The good thing is now, that you can modify your midi-recording prior to this playing through your rev2. I understand that this is what you are looking for.
You can, however, also have your rev2 be controlled (not the notes played, but the parameter settings) from Ableton. For that goal, you would want to install a VST plugin.