You can go the midi route if you like, or you can simply use one of the loops as a momentary switch and connect that loop on the GCX to the TF via the aux switch ports and set it for tap tempo.
That's the way I have mine setup now because I have 2 factors and trying to do preset changes and midi tempo from an external controller is a pain. So I keep tempo stuff via aux switches and change presets via midi.
Good luck,
Sean
