Music System

My San Jose Eichler (Westgate) has what looks like a fairly orignal outside music system. There's a grill with a volume control in the atrium, one near the utility closet in the back yard, and maybe one more, I forget.
The grills are painted over and I haven't been able to get to the area of the garage where the atrium one is located to check on the presence of a speaker and wiring. With just the one control, it's definetly a music system versus an intercom.

Has anyone else seen this? I think it would be cool to put an auto speaker behind the grills, repalce the volume control and hook it up.