[Impossible]

AAA game studios have 100s of artists toiling away at Maya and ZBrush, so I guess that means there isn't a working generator for computer graphics either ;).

In this case the author is using math to paint shapes and fill in colors, but the wider scene composition is authored. The equivalent of this for music would be hardcoding music composition/sequencing using code and writing procedural synths using math (like http://www.shadertoy.com music shader!), not a server somewhere generating music with no human involved.

Entirely procedural music is a genre though, as far as procedural music being "believable" (I guess aesthetically pleasing?) for you it probably depends on the right artists coming along and developing a sound you like, moreso than it not being possible.