I hadn't thought of that. That's a good idea.
I actually haven't really thought through the idea very much at this point. Basically, I started to think about it because I'd like to mirror my system at my dad's house. This would give me off site backup (and testing of the HDs, RAID 5 at each location.) The only issue I see is that we would then be sharing our CDs. At least on the ethical side, it would seem that if one were to make sure that no track were being played at each location, that you wouldn't be violating the copyrights. (Sure, I could just figure that nobody will say anything since it's all within the family and I'm not sharing with the world, but if I can do it correctly, I'd feel better about it.)
My initial thoughts would be to have the computer perform a query over the network (for now, I'm going to assume that the computers can speak over the network, ports can be tunneled using ssh from one location to the next.) Then you'd simply let the program know the addresses of the other machines and presto, it goes to the next song, checks to see whether or not it's playing on the other machine and if not, plays it. If it is, it skips to the next song.
kiwi