Regarding Depeche, people on Youtube have broken down exactly what each band member was playing during the 80s shows; you might find it interesting. The parts are simple. I don't say that to knock them at all, on the contrary it shows that pianistic excellence has little to do with great synthpop. Alan Wilder is a trained pianist and found little scope for his talents in those shows.

Of course the fast, repetitive bits were either on tape or sampled into the Emulator keyboards.