A problem particularly with my Rift because there is no hardware volume control. I can set the volume in Options but I often find it's a bit too loud after a few minutes of an online race. My hearing has been damaged enough already without rFactor making it worse. It's odd that there are bindings for Music Volume Up/Down (which AFAIK does nothing) but nothing for the sound that is actually heard. Ideally have bindings for the other volume settings too so they can be set while driving rather than the tedious Set volume Option. Drive car. Escape. Tweak volume Option. Rinse. Repeat.
I miss a volume control too since I use a headphone plugged direct in the PC. The bindings for music is for the Steam music player.