I told @P_T on irc that you could use this example as a base :https://alexgibson.github.io/offlinewebaudio/
It's basically what i said : Encode the audio as base64 data, decode it and play it back with the Web Audio API.
He told me he was happy about it, even though most people would prefer to use streaming over that of course.
(since they can protect it and encrypt it more easily)
Also, you cannot stop me if I play it and record it (using a different device) while it is playing.
Also known as the (anal)ogue ass
That's why Hollywood resorts to DMCA letters these days