Stage music
In the Super Smash Bros. series, each stage has one or more music tracks assigned to it. In Super Smash Bros., Super Smash Bros. Melee, and Super Smash Bros. for Nintendo 3DS, each stage has default music that will always play under ordinary circumstances. Certain stages in Melee and all stages in 3DS have alternate music that can be forced to play, or otherwise has a rare chance to play.
Super Smash Bros. Brawl introduced the My Music feature, which gives each stage a pool of music to choose from; the chance that each song has to play can be adjusted manually. This features returns in Super Smash Bros. for Wii U and Super Smash Bros. Ultimate. In Ultimate, stages from the same series share the same pool of music; additionally, the default settings for each stage have one song set to the highest and another song set slightly lower, in effect giving them default and alternate music.
In Super Smash Bros.
Super Smash Bros. is the only game without alternate music, so all stages only play their single assigned song.
In Super Smash Bros. Melee
In Super Smash Bros. Brawl
In Super Smash Bros. for Nintendo 3DS
In Super Smash Bros. for Wii U
In Super Smash Bros. Ultimate