This mod allows you to randomize various things in Sonic & Knuckles Collection. Level order, Special Stages, music, monitors, and sound effects can be randomized. For more information consult the help text at the bottom of the mod's configuration window.
You may download an extra music pack for the "Random" mode of the music option, including music from Sonic CD (2011), Sonic 3D Blast (Saturn), Sonic R, Sonic Adventure DX, Sonic Adventure 2 Battle, Sonic Heroes, and Sonic Mania. Extract the archive into the mod's "Music" folder to use these songs in the randomizer. You can also add your own music, read the readme.txt in the Music folder for more details.