The below work with playTrack. Try them (load straight into the command playTrack in the interface.
- 'http://s3.amazonaws.com/smartapp-media/sonos/bell1.mp3'
- 'http://s3.amazonaws.com/smartapp-media/sonos/dogs.mp3'
- 'http://s3.amazonaws.com/smartapp-media/sonos/piano2.mp3'
- 'http://s3.amazonaws.com/smartapp-media/sonos/lightsaber.mp3'
- 'http://s3.amazonaws.com/smartapp-media/sonos/alarm.mp3'
- 'http://s3.amazonaws.com/smartapp-media/sonos/the+mail+has+arrived.mp3'
- 'http://s3.amazonaws.com/smartapp-media/sonos/a+door+opened.mp3'
- 'http://s3.amazonaws.com/smartapp-media/sonos/there+is+motion.mp3'
It should do anything that you can link to as a url. Conditions: It must play in your browser (good test). Risk: some MP3's may not play due to internal parameters (i.e., bit rate). This is a device limitation.
However, to work best, I also like a different format for the data, and that appears to be broken. I will check further.