The Experimental Music Studios of the University of Illinois at Urbana-Champaign has released an four CD set in celebration of their 50th anniversary. The music is freely available as mp3s.
There is also a paper on the history of the center by Emanuele Battisti: The Experimental Music Studio at the University of Illinois, 1958-68: Environment, People, Activities, and one can find more history-related stuff if one looks around the site.
Lejaren Hiller created and directed the studio during its first ten years. He left in 1968 when he was appointed professor of composition at SUNY at Buffalo, and his archive belongs to the SUNY Music Library. The inventory, together with a brief chronology and bibliography, is compiled by Pei-jung Wu (this resource will be added to the EAM meta-bibliography).