no you can redo the tempo - within reason - too drastic a change mighr cause distortion and odd noises.. I've done it but can't remember exactly what you have to do - I think you just change the tempo in the tempo setting and RB looks after everything else. not in front of my music computer so can't test but just give it a go by simply changing the tempo. RB will guide you if you have to select certain tracks etc but i don't think you do. bear in mid that depending on how many tracks you have its quite a feat of computing to process everytthing so it may take a while but you'll see everything happening.