MT5 is a multitrack player based on the Web Audio API. It’s open source, runs on multiple devices (all recent desktop browsers except IE, all IOS browsers based on Safari Mobile, Android Chrome, Opera and Firefox mobile). It has been entirely developed in a web browser using the Cloud9 online JavaScript IDE. A demo version can be tried online at http://mt5demo.gexsoft.com while another version that proposes rock classics song by original artists has a restricted access (http://mt5.gexsoft.com).