One idea I didn't end up going for by heavily considered with my pechakucha was for the two songs to promote completely opposite readings of the vid – so if song 1 were "there's a hero who's going to save us" then song 2 would be about corruption, or despair, or "we can only rely on ourselves", or something with a contrast to the first song. And then check for the song on YouTube to see if the copyright demons are instadeleting all of it.