pitch bend, pitch bend and once again pitchbend .. but not on "per clip" basis, that's meaningless as someone pointed out, the stuff are allready warped, but on the project master tempo ..
well, it's not really pitch bend as you do with turntables, even if the primary goal is the same, to push a record to get in beat, and in this case without retriggering clips or using a controller to change the tempo back and forth and totally loose the contact with the audience, with a button i can simply push the tempo forward momentarely and catch up with a song on my turntable ..
a momentary tempo switch maybe it should be called .. i described it here (link) together with some other stuff that in my case would be a great improvement .. it's easy to program, and invisible to daw purists as it would only be visible in midi/qwerty assign mode ..
http://www.ableton.com/forum/viewtopic.php?t=49515