Thanks to JH for this one: Ishkur's Guide to Electronic Music is a great website explaining the evolution and origins of the many genres of dance music. It has some great visual diagrams mapping out the history of all kinds of dance music, with many audio samples for each.
I'm still not sure exactly who Ishkur is, but his intentions are pretty clear:
"To try and pinpoint the exact origins of electronic music, you first have to look at how it's made. Because as amazing as it sounds, electronic instruments did not always exist. The vast majority of them are barely more than 20 years old. And it's not like you can just pick up a sampler, synth and drum machine and jam away. Unlike conventional music, electronic music isn't played, per se. It is PROGRAMMED. So any study of the history of electronic music is really a study of its programmers--that is, the people who make the machines that make the sounds that make the music what it is. Without some guy tinkering with diodes and transistors, electronic music is just a fancy, lifeless hunk of junk. Just sitting there. Not doing anything."