Playing background music for players is more a function of Teamspeak than it is any addon in FG. Not that the addon isn't wonderful, but it's not necessary for playing music over TeamSpeak. Once you've installed the Cable output for your sound system, just set it up as your default playback device, and open your sound program. Then load the cable output in a new tab in TeamSpeak, and you're ready to play for everyone.
Now, if you want to set up automation so that your hit/miss/crit/fail sounds happen without your intervention, that does require the plugin/addon that these guys built. And it's cool.
But it's really easy to use iTunes or whatever to play sounds to your players. Go to the FG wiki page on Setting up syrinscape with teamspeak for more info.

