You could do the same thing with a .wav file, embedding the HTML after the data ...

jschwartzi · on Aug 10, 2016

WAV is actually a specialization of an old container format called RIFF. RIFF allows for extensibility by allowing the embedding of arbitrary data.

So this is technically a legitimate use of RIFF because it's designed to support multi-purpose contents, not just PCM data.

voltagex_ · on Aug 11, 2016

Aha! This is how Beatport were putting title/artist data in WAVs.

I'm not sure why they did that instead of just sending FLACs, though...