This is like having a Rock and Roll Music thread. There's too much to discuss. On the other hand, too few of the names mean anything to even a minority of most people. And I'm pretty under-informed as a guide.
Let me toss out a few more names as a start.
Iannis Xenakis - not exclusively electronic but a profoundly influential cyberprophet who helped make music 'algorythmic' (my own dumb term coined this moment) applying all sorts of newfangled mathematical and engineering and architectural principles to musical composition in order to see if the results in any way matched his expectations, the very definition of 'experimental music' in its scientific aspect as opposed to its totally free form improvisatory one. He has inspired the fields of computer design and architecture as much as they inspired him. Plus, his fingerprints (and those of closely related or propinquitous folks) are all over Revolution Number Nine (I believe!)
Luciano Berio's early electronic phase
and Berio's vocalist muse and wife Cathy Berberian: The pitch perfect diva of avant vocalizings: sorry Yoko and other contenders, but she screamed, clucked, and moaned louder and better first. She could also sing opera as good as nearly anyone, AND sing the Beatles as if they were Mozart. Anyone ever heard this (possibly hugely misguided) record??? I want to:
http://www.franklarosa.com/vinyl/Exhibit.jsp?AlbumID=73(edit: the link's unstable. Do a google search for ...Berberian Beatles, and pick the first selected site by way of 'cache': the realplayer stream will work)
Save that for later (though listen to the audio link right now: I approve totally despite what the commentator at that site says: this is good humored not unintentionally funny). What you should find first is Berio's electronic-sound-accompanied collage-montage of Berberian improvising on a single word ('Parole' ='Word'), "Voices" from 1961 or so. Its incredible. Steve Reich's early voice-electronics stem from this experiment and others like it (Reich's own "It's gonna Rain" and "Come Out", however, may represent the absolute acme of the form, trance music that is consciousness raising as well as mind altering, the former about the Cuban Missile Crisis and Nuclear Rain (like Dylan's tune), the latter about Civil rights and black people bleeding. These are intensely beautiful and unsettling 'trips', the more a speech fragment's repeated and refracted the more abstractly beautiful AND profoundly weighty it becomes. Don't listen to me prattling on about these. Just run and buy them!)
Charles Dodge: lesser known name who I include as one who has mined the area described above more doggedly and thoroughly over the course of an entire career than anyone else, a fine master of "electro-acoustic works incorporating speech synthesis." (characterization from
http://www.cdemusic.org/artists/dodge.html). He was also my Music Humanities teacher freshman year in college, and a very good one.
Don't forget John Cage, not so much as a hardcore electronicist (though he helped popularize tape loops in his performances), as for his oblique strategies and selfstyled Buddhist-dada. Eno stands on his shoulders. Another Revolution 9 companero of Lennon's, the flipping of the magic radio dial aspect.
Oh, and the couple that scored FORBIDDEN PLANET, Louis and Bebe Baron, supplying 'electronic tonalities'. Definitely buy the soundtrack and read Bebe's interview in Extremely Strange Music, vol. 2. It's clear the pair believed the gizmos they were creating to make the sounds somehow achieved 'living status'. She describes what they did for the tape recorders as the death cries of little guys having their circuits overloaded! (or something like that)
And re: the bunch of them, my intro to this all was via Zappa's comments on Varese which sent me running to pick up the several samplers of electronic music then available, all with futuristic covers: a red oscilloscope tattoo; a 2001 sterile white musical laboratory, and the like. Varese has already been mentioned but the opening of Poeme Electronique should be underscored: that Big Ben-like bell tolling has kept tolling through many other artists' tracks over the decades, including Lennon's.
That was a start, but it was works in performance that made it all make sense for me, or part of it all, the Robert Rauschenberg-Fluxus-Cage spectrum of Happenings, and much later seeing Kraftwerk. (the other part was works whose spectacle was aimed strictly between the ears: the headphone music)
My real guide through all of this was a friend of my parents who knew the whole electronic crew and allied visual artists like Paik and who specialized in doing visual art in concert with them, literally sometimes, more often in extremely labor-intensive multi slide and movie projector picture shows (images being cross faded and superimposed etc. etc.) scored and D.J.ed very precisely to pre-recorded tracks by the musicians listed above (and sometimes his own). I'm glad I saw every single one of his performances because they died the moment the lights came up, and his life's work died with him (luckily, I snagged three or four of his fifties mounted collage works on paper, which he'd taken pains to destroy, just not quite enough! I'm glad to have the mementoes, but I've incurred some bad karma I'm sure in destroying the purity of his self-immolating Buddhist flame!)
EDIT: How convenient, Brian Eno backs me up on several of my musical choices. Listen to samples on his 'early gurus of electronic music' anthology cd (that OHM collection referred to above, brand new to me, thanks for alluding to it) here, though he should have dropped the Eno and Hassell tracks (early gurus???Though I admit the tracks chosen show them as very interesting sums of the parts preceding, latterday syntheses suggesting ways beyond the past ) and included an early Steve Reich instead even if it had to take up the entirety of a side! What the collection doesn't and can't get into for practical reasons is that early electronica was often a very, very long form deal (or ordeal), or Steve Reich at all. He remains the greatest artist with broadest possible ongoing relevance of them all defying labels like electronic and minimalist as fast as you throw them at him as far as I'm concerned:
http://www.amazon.com/gp/product/B00004T0FZ/sr=8-19/qid=1139808539/ref=sr_1_19/104-8916806-0151906?%5Fencoding=UTF8And one more EDIT: why is Steve Reich so spottily repesented on CD, and where can one find those famous tracks of his I mentioned above?