[andkon]

This was like five years ago that I had one, but as far as I remember, OP-1 isn't grid-based (though maybe some of the instruments are?). It's basically like a four track tape mixer. You can loop bar-by-bar, and then copy from bar to bar. And you can stretch time in the same way that you would with a reel-to-reel tape deck. But as far as I remember it won't transpose / warp the sounds along with the change in BPM.