”Owners of Steambikes that currently have unique music playlists installed will receive the Music Discs with their Steambikes music. From now on, to listen to the music on their Steambikes they will need to use that Discs so Subwoofer skill would be activated.” (Link)
If you have an M1 steambike (the maximum tier version) when we added the music disc system the bike lost its special music. However you can do a revert craft on the bike which will then give you the music disc with its custom music back.
Correct. Maxxed M1 no longer supports music, but when you revert it back to Maxxed you'll automatically receive a Disc with the music you could play on your M1 with it.