Right... "We're all playing together now, children." Just sayin' it does sound straightforward but, in practice, not so much for some. Requires more listening, as opposed to playing. I know I can struggle with that sometimes.

These two guys (El Ten Eleven) definitely seem to have some sort of click or guide track in their earpieces. You can see how they check in with eachother before starting the song.

Of course, neither of them is playing a modular. They are each sampling and looping while playing their respective instruments. I would also venture to say that neither of them is leading the tempo. They both seem to be following the guide track. Yeah... they're practiced.