Part of the enjoyment of the web is tracking down stuff you know absolutely nothing about. Of course it helps having good guides, and I stumbled on this via Simon Reynolds blissblog who refers to an excellent survey on this scene by the stupendous woebot.
Variously called electronic music, modern classical, contemporary classical or experimental music this collection was originally released as a 2-LP boxed set as in introduction to and survey of electronic music, circa late 1960s. All work realised on the Moog Series III Synthesiser.
Wikipedia on Nonesuch:
Nonesuch Records is currently allied with Warner Bros. Records even though it is an Elektra Records subsidiary. Jac Holzman, founder of Elektra Records in 1950, founded Nonesuch in 1964 to license European classical music. He sold Elektra and Nonesuch to Kinney National Company in 1970. –http://en.wikipedia.org/wiki/Nonesuch_Records
Nonesuch also released Silver Apples of the Moon.