As stated, audio should not give additional feedback to the player. Does this remove the possibility for mood music/ambient sounds?

As long as the ambient music does not switch to indicate something you can't understand, it should be fine.

For example: a blind brick breaker game (idk) can use background music, and if the game has flashes to display if a break was broken, i think you can add an audio queue to symbolize that only.

Hope that helps.