protosong
Noun. In music a “protosong” is an early version of a song. As opposed to the traditional "demo version,” a protosong is less a demonstration of a already composed song and more the seed that grows into a particular track.
I was listening to the protosong of The Stooges' "I Wanna Be Your Dog." It had the riff and chord progression, and Iggy yelped the chorus; still, you could hear all the basics.