Not in Logic 8, but you can in 9 with Flextime. BTW, how much does the tempo change in percentage or BPM? Across how many tracks? Does the tempo change wreck the groove? Someone posted recording to a click, that's not a bad idea, but not all drummers can play to a click. The most important part of any song is making sure the basic rhythm track is SOLIDLY in the pocket. If it's not, you are building your house on a shaking foundation. Of course it may be ability too. In that case you really need to get Logic 9 and lock that thing to the grid.