Would love to be pointed towards anything new and at least as good as MilkDrop!
Note: you don't need the retired Winamp player, as e.g. foobar2000  with the shpeck plugin  runs MilkDrop perfectly.
Take a look at this.
Unity being used in realtime with a pepper's ghost projection.
I'm excited to see how the next generation's Michel Gondry uses new tech like style transfer and procedural design in creative and non-obvious ways.
I'd be interested to know if this is running solely by analysing the audio or if they have access to a MIDI file or similar that gives cues as to each sound. I know that the ability to process and recognise individual sounds is becoming ever more powerful, but it would be an easy shortcut to have a MIDI file generated by the sequencing software to give cues for each specific piece of landscape (as they all seem to be tied to a given sound, and then have variations in their appearance depending on that sound's specific pitch).
It's added another thing to the "list of things that I think I should know how to do"...
https://www.youtube.com/watch?v=_z-_3ffgz8E <-- Here's one I did a long time ago (and uploaded not all that long ago). Things one could do with this: transition the background, play with the camera, transition colors, separate out the SID's three different tracks. (Note: this raytracing algorithm only works with square column grids, but is pretty fast, as it's very easy to work out where a ray will hit. (Maybe it could be done in real-time at a low resolution using modern hardware.))
I really enjoyed MilkDrop back in the day. It seems like hardly anyone is interested in visualizations anymore. :<
I've been following an artist called Raven Kwok for a while. IMO his generative work is much more interesting, and a better contender for "state of the art."
it's a very nice work.
I feel like use of the term "procedurally generated" is an effort to conflate a degree of complexity beyond well-known, existing graphics techniques not available in common software.