OK
PlaySound returns a handle to that sound (or 0 for error).
Once playing you can adjust volume and pan on that channel.
setPan(chan, amount);
setVol(chan, amount);
setMute(chan, value);

Another pretty standard item is the mute switch. Lots of cool effects to be had with one of these...
Ultimately you want to build a sophisticated sample playback system that includes pitch and even envelope control... later down the track maybe?
setPitch(chan, amount);