Master player is located at the top of file page. It is controlled by blue play/pause/stop buttons. It plays master MP3 with reverb applied. On the contrary, multitrack and single track players do not have reverb applied and sound dry.
Master player mouse actions:
Parts tab (multitrack player) allows you to change instrument volume and panning live and solo any combination of tracks. It has to load all tracks into memory until you can start playing. This means that you have to wait until all tracks are loaded, which can be long on slow internet speeds and can take lots of traffic. When total time of tracks to be loaded is significant (e.g. more than 150 minutes), browser can crash trying to load them.
Here is what you can do to improve multitrack load speeds and prevent browser from crashing:
Multitrack player mouse actions:
Solo parts tab allows you to listen to each individual track. It does not have to load all tracks and thus can start playing right after the page load.
Single track player mouse actions:
Space bar - play / pause player