Have you watched a certain video online and wondered "Wow, wish I could listen to that cool music in game" Here it is. It isn't the complete song, because I edited the parts down to fit in a heist track.
The stealth music is the joker by the Steve Miller Band. https://www.youtube.com/watch?v=h66V1hYAjG0
Put the folder in your custom OST tracks in your mods folder. Must have Custom OST mod.
