The player in Music Collection is JW Player.
This player is one of the most stable and HTML5 players on the net.
This player plays MP3, but also AAC, MP4 and FLV files, and thanks to the built-in Youtube Video integration in Music Collection, it can play YouTube videos too.
Besides of the plugin loaded in every page of the component, all Music Collection modules include it in order to place them and being able to play their songs even outside the component, anywhere in your site, so your users can listen to songs while they are browsing your site.
Using the playlists module, users will be able to load playlists on it on-the-go, add songs to it, etc.
You can adjust the player parameters to have the skin, size, playlist.. etc you want.