It adds a custom music heist track for payday 2
It goes like this:

Stealth: Red Bread https://www.youtube.com/watch?v=RBRlXsSXzCg

Control: Tf2 main theme smash bros remix https://www.youtube.com/watch?v=W3_vfTsDRdU

Anticipation: Tf2 main theme smash bros remix (a bit edited)

Assault: Tf2 theme rock cover https://www.youtube.com/watch?v=QyJZ0dVeCtw

To install simply extract the file inside the rar to mod_overrides

Credits: Valve Studio Orchestra (all tf2 original songs including red bread)
SuperWiiBros08 (tf2 smash bros theme)
Friedrich Habetler Music (tf2 epic rock cover check out his channel pretty cool)