Might be of interest a system that I've been used wich is:

I've built a Box where a button can be pressed in case the visitor wants music.
In the same box there is a small written introdution to the theme. The rooms,
wich
in general are small/medium size there are 4 speakers wich give a good
ambience to the room.
Inside the box I have adapted an auto cassete player connected to a
watch-switch
wich after 1, 2, 5, 10 minuts (depends on pre regulation) automaticly switches
off.
Sound quality is acceptable and the system has been working perfectly for more
than 2 monthes now.

Emanuel