In Digital Performer I can lock midi and audio so that if I decide to make my tempo 75 instead of 150 I can and things don't shift. I was trying this in Logic and couldn't make it happen as the lock feature isn't the same. Maybe there's a preference or maybe it just isn't possible. Why was I doing this? I was trying my new drumcore 3 plugin and the song was done in 150. But, the actual groove, where dc didn't sound crazy, was at 75. So, I had to slow down logic to audition the (in this case) midi groove. Then, speed up logic, drag the groove in and then time stretch the midi groove (which is very cool, dp can't do that!).