Okay, at some point this counts as improvised. We're talking about lyrics, percussion, bass guitar and other instruments (at least in the case of Blurred Lines, where the writing of the lyrics and instrumental tracks were what was in question). Assuming you have only two hands/ears with which to write/play with the sound of, that's writing at nearly 1/2 the speed it is performed (and could be considered near-live writing if you aren't da Vinci'ing it).