There is a checkbox now that reads Plays Audio Files and has the same icon that is now used for signaling the new audio clips. I'm sure there will also be a few users that will wonder how that differs from Background Music.
Agreed. These are three things that are very different to a skin developer, but to a user, are all just variations on a theme. Maybe we should just decide that Plays Audio Files
means that the skin can either take an MP3 as an AO in and of itself, or as an audio clip that's attached to a JPG. Background music is sufficiently different that it can perhaps retain its own checkbox.
Well, sometimes it does. Depends on who's developing the skin.