It has 4 dedicated sequencers. They're locked to whatever tempo the metronome is configured for. You can mix durations pretty fluidly with the endless sequencer (8th, 16th notes/rests), but you definitely cannot change tempo in a given beat--at least not without jumping through a bunch of hoops bouncing and re-recording tracks, etc. There's a basic grid type sequencer as well, but that doesn't meet your criteria.