It is bcline’s wonderful player as seen in Sources/Experiments.
This player is autoplay and myself and other’s on the author’s blog are wondering how to disable autoplay for obvious reasons. The author is a very busy student and is unlikely to have time to rework this player anytime soon.
I personally would be happy to leave autoplay but have the volume start at 0 so the user would see the song title/duration and be tempted to drag the volume button to listen.
I also have this question on Experts Exchange with a 500 point value.