Well, since SOMEONE has to pipe up and say Pd can do it, might as well be me. :)
Pd with GEM is pretty cool as far as visualization goes. Far better than anything I've ever seen or heard of actually, because you can visualize MIDI any way you want, which has waaay more potential than visualizing a boring old waveform (digital audio)
I'd say the opposite is true. Midi is lame for visualizing a continuous data stream, say for example mapping frequency content or amplitude to a continuous visualization. While midi is easy to work with with, 7-bit cc values are pretty coarse. The trick to making the waveform visualiztion interesting is to allow the user to break up the composite waveform into user defined frequency bins so you can ride the amplitude of specific frequency areas.
Iain
But you have lots of continuous controllers, is it 31?, and they control 16 channels seperately, and on each channel you have identifiable intruments playing at different times. This is a much richer stream of musically relevant information to display than just what you can derive from the output signal.
Greg
