This patch will make so when pausing, the level's song keeps playing but with a lower volume, and then restore the normal volume when unpausing/exiting with select. Check out the readme for instructions on how to use it, but keep in mind that you must use AddmusicK to make it work.
For a better effect, you can also pair it with the Darken Pause patch.
v1.1: now compatible with all recent versions of AddmusicK (1.0.6, (partially) 1.0.7, 1.0.8). Make sure to read the readme.