Synchronizing MP3 players is darned near impossible, at least from what I've been able to determine. I suppose, if you get deep enough into the guts of the player, you might be able to do something, but all the plugins I've seen to add this to, say, Winamp, drift apart eventually and never get perfectly synchronized

A good point, and one we hadn't previously thought of. But presumably, for Receiver purposes, they needn't be that synchronised. We could sync them up at the end of every track; clock drift during one track is a probably-inaudible amount.

Peter