Hi.
I use the AR as a drummer. concretely : In a hybrit-drumset i triggere with pads (mashheads) via a drum module (Roland TD-20x) the single tracks and scenes of the AR and with a pedal single parameters. I also use one pad via MIDI clock to tap the tempo of the AR. so far so good (the sound is stunning, the audio out of the drum module is still unplugged 
(with the exception of the toms ), only my jomox mbase 11 continues for the second kick.)
question 1 : Unfortunately I have not found a way how I can activate the sequencer (start / stop / rec) via midi (the simple problem while playing drums: usually both hands and feet are otherwise in use)
Question 2 : with an extern midi clock signal the bpm in AR wobbles between +/- 0.5 bpm back and forth. Maybe its an ordinary Problem for everyday midi users? Iām still surprised.
about an answer I would be very happy . best regards helmut