It is plausible that banger, in the current sense of a successful song derives from the above meaning of headbanger. The idea is of a successful piece of music to which rhythm people move and dance. It's like banger after bangerit means something is a great hit, awesome after awesome|@gmz02344 not exactly.

This song is a bangerit means the song is really good. Banger is slang for good music. |when a song is good you rock your head to it, head bang, or bang on things around you like a drum. The song is so.