I can base something off what SamStone said.
As an obscure hip hop band, I like what Audible Mainframe has done with their two tracks, "Ice Cold" is $1, while "Anybody Else" is the typical $2.
Music scavengers (like me) are willing to purchase $1 songs from bands they don't know about but sound promising to their ears. If they fully liked the song, they would end up feeling more confident about this band, and purchase their $2 song. Means more revenue for the band than with 2 $1 songs, or maybe even 2 $2 songs.