[kevingadd]

Mozilla had procedural audio generation through <audio> with a simple, documented API back when Chrome couldn't even play non-procedural audio through <audio> properly.

http://phoboslab.org/log/2011/03/the-state-of-html5-audio

Procedural audio is also effectively a corner case compared to the vast majority case, which is playing static sounds.

[comex]

Simple, documented, and slower - you had to do everything in JavaScript. Web Audio API retains the ability to use JavaScript but provides a nice set of fast primitives.