On this subject, a while ago I thought a cool feature for the MAME developers to add to MAME was a DISABLE GAME MUSIC switch. To implement this, each game would need to have the music channels flagged as being music channels, and these would be disabled if in game music was switched off from a front end etc.
Some games I'm sure would use the same channel for music as well as sound effects (I think Gaplus or one of the early Galaxian type games) which may require some extra programming in MAME, but I think it would be worthwhile feature, especially for games with traumatising/epilepsy inducing music, or if you wanted to play your own MP3 playlist while playing them.