Greg MacAyeal first encountered John Cage while studying music composition in the late 80s as an undergraduate at the University of Illinois at Urbana-Champaign. Arguably America’s most influential experimental composer, Cage is famous for his 1952 “silent piece” 4’33”, and in the 1950s and ’60s he’d pushed the envelope musically by composing works incorporating silence, indeterminacy, and electronics. He’d taught and researched at UIUC two decades before, from 1967 until ’69, spending most of his time cocreating a mammoth computer-music piece called HPSCHD that premiered in May 1969.

Wesleyan University holds documents related to most of Cage’s books, the New York Public Library holds most of Cage’s music manuscripts, and the University of California, Santa Cruz, holds Cage’s materials related to mycology (the study of fungi). But the collection at Northwestern is the largest single concentration of Cage materials anywhere in the world—it not only surveys modern musical composition during the 1960s but also humanizes a composer who continues to divide scholars with his challenges to the definition of music.

In 2013 Northwestern hired Ryan Dohoney, an assistant musicology professor who teaches on Cage, his New York School collaborators, and experimentalism in music at large. (Full disclosure: I’m a junior at NU, and I’ve taken two of Dohoney’s classes. He also advised a grant-funded research project of mine last summer.) One of his courses focuses specifically on Cage, his relationships with collaborators, and performances of his works—it draws from materials in the collection, and according to Dohoney the music library’s staff has been integral to making it happen. “They’re so open to me having people dig through it—students who don’t know anything about a) archival research or b) John Cage,” he says. “It’s this way to orient them to real research with some of the most rewarding materials of 20th-century music.”

The Notations Project Collection includes scores to many other compositions revered as technical achievements, such as Steve Reich‘s 1967 Piano Phase, his first major piece for live instruments that employs the technique of “phasing”—two pianists play a simple, rapid figure in sync, and then one speeds up slightly, causing them to slip out of alignment and eventually back into a new one. Cage’s close contemporary Morton Feldman sent in 1964’s The King of Denmark, his first graphic score. And Cage’s own contribution, the 1951 piano piece Music of Changes, was one of the first to employ indeterminate methods in its composition—his original copy rests in a book-shaped box, black on the top and bottom and red on the sides, with each page separately laminated.

In contrast to the Notations side of the collection, which brims with the sort of puckish musical unorthodoxy that Cage found fascinating, the Correspondence Collection more fully expresses the composer’s ordinary, relatable humanity. As MacAyeal says, he was “a man who had likes and dislikes and friendships and felt pain and felt joy and had setbacks and successes.”

John Green, a PhD candidate in musicology at the University of Rochester, knows something about the possibilities the collection contains. His dissertation research focuses on four of Cage’s broadcast pieces, three of which—his music for Kenneth Patchen’s 1942 American radio play The City Wears a Slouch Hat, the 1979 West German radio performance Roaratorio, and his performance in Nam June Paik’s 1984 international satellite-TV simulcast Good Morning, Mr. Orwell—figure extensively in the Correspondence Collection. Green won Northwestern’s $3,000 John Cage Research Grant in 2017, which funded a visit to the collection. He found letters from listeners responding to Slouch Hat, Cage’s letters requesting sound recordings for Roaratorio, and letters between Cage and Paik planning for Mr. Orwell.