Here’s the electronic version of Stockhausens Kontakte from 1960. There’s also some interesting text comment in the beginning.
There a version of Kontakte including piano and percussion.
Ian Halliwell has made a fantastic series of radio programs called The Tone Generation exploring the early days of electronic music roughly 1950-1970. He uses his personal collection of records and cds, looking at different themes and composers in the era of analogue tape and early synthesizer technology.
There are now 20 programs available at blip.tv, where the initial 10 part series was first transmitted between April and June 2008 on Resonance FM. There are programs covering major composers from influential countries but also other themes like the EMS and RCA synthesizers, female electronic composers, jazz, dance and the Expos.