In Sonic & Knuckles, as well as other Sonic games of the Genesis era, the title screen would often be the source of the Main Theme used in the game. In the case of this game, the theme is used for the title screen, collecting a 1-Up, becoming invincible, and clearing the game. These themes are also used in place of Sonic 3's versions when this game is locked onto it (which produces the game known as Sonic 3 & Knuckles). All variations of Sonic & Knuckles' main theme used in-game can be listened to below.
Title Screen Edit
Game Clear Edit
For the game clear jingle, please head to Sonic & Knuckles - Credits, which will be at the end of that song.