So that is what the difference is in the Conductor and the Slave? I just finished putting them both together and took a look around but could not find a definitive answer as to what the purpose of the slave was.
Yes, the slave as Rick said doesn't have a clock so it doesn't have the ability to run its own schedule or audio output. Instead, it listens for something (the Conductor) to tell it what show to play and when to start. The Conductor then sends a timing (heartbeat) signal every second to make sure that the slave(s) stay in sync with the Conductor. It is also called a heartbeat signal because if the slave misses 6 or more of these heartbeats, it takes that as the Condcutor stopped and stops it's show as well.
Since it depends on simple control signals for operation, it would work well for what Steve wants to do and would also work very well with the software mykroft is working on. And as with the Conductor, if the PC locks up and stops sending control signals, the slave unit(s) will also shut down in about 6 seconds.