I take that back - after consulting with my hubby (hi, we're dorks!), I do think the Cylon fleet they jumped into were broadcasting that music.

The fifth, in my opinion, anyway, must be Starbuck b/c the fifth humanoid didn't meet up with the others on Galactica because it wasn't on Galactica. It/Starbuck was finding Earth.

That's my theory and I'm sticking to it. ;)