This can be used for whatever, but please give me credit. I used the boss intro song from MM2, but you can really do any song, just put the song in the backdrop sprite and put the play song block in between the variable blocks. This is a huge improvement from my very early projects (on the offline app a few years ago) because I used a variable from the backdrop instead of wait blocks and repeat ___ blocks on the boss intro sprite.
I got the boss intro thing from a gif, but I forget where it came from. Credit to that guy, then. @-MegaManMM7- for the music that he got from Khinsider.