Milly vanilli

As I bounced up and down trying to lull Joshka into a sleep-ready state, singing "Twi-i-nkle, twi-inkle li-itle sta-a-ar, ho-ow I wo-onder wha-at you a-are..." I just couldn't get out of my mind how pop stars manage to sing on stage - live - while cavorting all over the place. How can that somersault/kick/jump/shimmy not affect that note?
They must be faking it.