For my first custom track I decided to take the music of one of my favorite composers in the "synthwave" genre - Perturbator. This override-format modification contains two tracks of Perturbator: Perturbator - Consecration (for stealth phase); Perturbator - Eclipse (for loud phase).
For this custom track to be played in your game you'll need to install the "BLT Hook" and "BeardLib".
Then just move "Consecration Eclipse" into your "mod_overrides" folder, which is in "assets" folder of the PAYDAY 2.
Done! You're amazing!