But the best MIDI-triggered visuals I did by far was the "Galaxy" stuff back in 2008, which involved a MIDI looper I wrote driving a MIDI visualizer system that used each MIDI channel to instantiate graphical sprites with different behaviours. I used it for only two live performances, and here are recordings of it. The first one makes the operation most obvious, where each instrument/channel is introduced gradually, so you can see the different visual behaviours of each channel clearly:
I think that that approach has a lot of potential. Using MIDI to trigger visuals is, IMO, much better than using audio, since you have a lot more specific data (channel, pitch, velocity) that can be used to control the graphics in ways that make the correlation to the music much more obvious. The second piece from that first performance was more ethereal/ambient, so the correlation of graphics to MIDI isn't obvious:
The second performance I did with the Galaxy system was an even more involved setup, taking the Galaxy visual output and feeding it into what eventually turned into LoopyCam (this video is sadly out-of-focus):
The right way of doing this kind of thing, nowadays, is to create a Freeframe plugin that accepts MIDI and triggers visuals within a Freeframe host such as Resolume. I have this kind of thing currently working as a side-effect of my Space Palette work. There's nothing I can distribute currently, unfortunately, but someday...