That's the only downside, the hotkeys. I'm sure I can speak for every SLRR fanatic and perfectionist who always get those perfect camera shots (myself included.), it's annoying always fiddling with the +/- and ,/.
Other than it's not *that* hard removing the songs from this game, or adding new.
This mod's okayish, downside being you're missing out on the game's amazing OST!

The game has music volume hotkeys: Numpad +/- (btw, there are also ,/. for previous/next track). The problem is that the zoom keys of the photo camera(F9) are the same.
Sure, deleting/moving the files manually would work, but I think using this item is more convenient.
Btw, the Custom Workshop Installer can save a list of installed mods allowing easy reinstalling later (feature added in Update 11k).

In-game; Options - Audio, music slider all the way to the left.
OR
steamapps\common\Street Legal Racing Redline\music - delete all
<3