On the right, you can play and record compositions.

When I tried opening someone's saved song in Firefox, the Play button did nothing. But it worked in Chrome.

At least playing my own records works. I don't have a link to someone elses so I can't test it. They seem to have slightly changed the player though, from the last time I checked. There was no arrow pointing at the keys for instance.

Adding to my previous: it works _and_ there is no upgrade notification.