I think the last 4 we've seen are cylons.
It' s not enough that they all heard the same music. If that were the case, then yes, the Cylons could have done something to them on New Caprica. Perhaps a radio implant. (Howdee music lovers! Your listening to W-C-Y-L-N, the toasters with the most-ers! ... and here again, our number one hit; "All Along the Watch Tower" by some band most of you hadn't heard before! but first this message)
But I don't think it was just the music. I'm pretty sure something else went "click" in all their brains. A switch being thrown off that returned the memory of their identities. I mean it's pretty out of the blue. "Hey we're all hearing the same music, must mean we're Cylons". That's a stretch. Something else must have clicked.