They may not have been able to come up a good song quick enough. Or his thinking is just that we use actors to portray characters, and props to portray vipers/consoles whatever, why not just use an existing song to portray a song they need in the show.
I'm also thinking that we are going to end up all by related. Orignal humans build cylons, who build skinjobs who evolve get rid of mechanical cyclons and start to think they are human. And later new humans/skinjobs build mechanical helpers and start the cycle all over.