Ryan Barrett wrote up his findings on his blog.
His solution involved using NTP as a method to keep all the clocks in-sync:
Seriously, though, there’s only one
trick to p4sync, and that is how it
uses NTP. One host acts as the p4sync
server. The other p4sync clients
synchronize their system clocks to the
server’s clock, using SNTP. When the
server starts playing a song, it
records the time, to the millisecond.
The clients then retrieve that
timestamp, calculate the difference
between current time from that
timestamp, and seek forward that far
into the song.