Michael Mitchell, his son-in-law and personal assistant, said the cause was complications of Parkinson’s disease.
Johnston was an unusual avant-gardist: His music was so melodically engaging, rhythmically vital and structurally transparent that listeners who were unaware of his tuning experiments and their complex theoretical underpinnings heard his works as essentially neo-Romantic.
In addition to using microtonality — a system in which the octave is often divided into dozens of pitches rather than the traditional 12 — Johnston sometimes used serial techniques, in which pitches were presented in a predetermined sequence. He invented his own notation systems to account for his tunings, which could change from piece to piece.
His 10 string quartets, for example, are dramatic, sometimes incendiary scores with hard-driving and often tense fast movements as well as ruminative slow movements — with occasional quotations from folk melodies. His String Quartet No.4 (1973) is a set of variations on “Amazing Grace,” recast in his tuning system, which gives the melody an antique, rustic sound.
Johnston created several stage works, including “Gambit” (1959), a ballet with a vivid, jazz-tinged chamber score that Merce Cunningham choreographed, and incidental music for a production of Shakespeare’s “The Taming of the Shrew” (1961).
His “Carmilla” (1970), an hourlong chamber opera about a female vampire with a libretto by Wilford Leach, proved a popular draw when it was staged at La MaMa, the experimental theater in Lower Manhattan, shortly after it was completed. So did his final stage piece, “Calamity Jane to Her Daughter” (1989). Based on the possibly fictional letters of its title character, the work is built around themes in a folkish cowboy style.
Unlike Harry Partch, with whom he studied briefly and whose microtonal tuning philosophy he expanded upon, Johnston did not build specialized instruments for his music. He preferred either to retune conventional instruments or to have players find his pitches between those they were used to playing.
His passion for microtonal music grew out of a desire for intervals that were purer — more fully in tune — than those yielded by equal temperament, a system adopted by composers in the 17th century that made it possible to produce a more or less in-tune sound in any key. In the system it replaced, known as just temperament, individual notes were tuned slightly differently in each key.
“Ben’s incredible mathematical imagination vastly expanded the range of usable harmony, diffracting music into new colors we didn’t know were there,” composer and critic Kyle Gann, a former student of Johnston’s, said in an email. “His Seventh String Quartet, probably the most difficult ever written, uses more than 1,200 pitches to an octave, and seems to float like an astronaut through free pitch space. Yet he never got too sophisticated to quote tunes like ‘Amazing Grace’ and ‘Danny Boy,’ and that common touch keeps his music grounded in the real world.”
Benjamin Burwell Johnston Jr. was born in Macon, Georgia, on March 15, 1926, the eldest of two children (his sister, Janet, died in 1999). His mother, Janet Ross Johnston, was a Sunday school teacher; his father was the managing editor of The Macon Telegraph and, after the family moved to Richmond, Virginia, in 1937, The Richmond Times-Dispatch. Young Ben briefly followed in his father’s footsteps in 1942, when he became editor-in-chief of The Jeffersonian, his high school newspaper.
Johnston had been drawn to music as a child in Macon, where he heard jazz recordings by Duke Ellington and Jimmie Lunceford and began collecting records of popular music. In Richmond, he began studying both the piano and the trombone, which he played in the school orchestra. In 1943, he won first prize in a composing competition sponsored by Scholastic magazine for a song, “Homeward,” and second prize for a keyboard fugue.
Before the end of his first term at the College of William & Mary in Williamsburg, Virginia, where he enrolled in 1943, Johnston presided over a concert of his songs, piano works and chamber pieces presented by the Student Music Club. He joined the Navy in 1944 and was posted to the cruiser Augusta. After he was discharged in 1946, he married Dorothy Haines, a singer; they divorced six months later, and Johnston returned to William & Mary, where he completed his BA in fine arts in 1949.
During a visit to Richmond in 1948, Johnston met Betty Hall, an art student at Richmond Professional Institute, on a blind date; he later said that they had talked nonstop for 48 hours. They were married in 1950.
Betty Johnston died in 2007. Johnston, who died in an assisted living home, is survived by their daughter, Sybil Johnston; their two sons, Ross and Christopher; and three grandchildren.
Johnston began working on his master’s degree at the Cincinnati Conservatory of Music, but he was disappointed in his composition classes. He decided instead to write to Harry Partch — whose book “Genesis of a Music” he found inspiring — to ask if he could study with him. Partch, though disinclined to teach formally, engaged Johnston as an apprentice on his farm in Gualala, in Northern California.
Johnston’s duties there included tuning Partch’s homemade instruments and performing on recordings of several of Partch’s works. He and Partch also collaborated on a theater piece, “The Wooden Bird.”
In 1951, Johnston enrolled at Mills College in Oakland, California, to study with Darius Milhaud. By the time he completed his master’s at Mills the next year, he had accepted a teaching position at the University of Illinois at Urbana-Champaign. He remained on the composition faculty there until 1983, when he became an emeritus professor. The university published a collection of his writings, “Maximum Clarity: And Other Writings on Music,” edited by Bob Gilmore, in 2006.
After meeting John Cage at a new-music festival in 1952, Johnston traveled to New York to study with him. He would work with Cage again during a sabbatical from the University of Illinois in 1959 and 1960, when Johnston won a Guggenheim Fellowship.
Among his works from this period were “Gertrude, or Would She Be Pleased to Receive It?” (1957), a chamber opera about Gertrude Stein in which satire mingles with elements of both popular and modernist music; “Sonata for Microtonal Piano” (1959-64); and “Music for Groups” (1967), which was given its premiere by the St. Louis Symphony Orchestra even though the players had rebelled in rehearsals against Johnston’s intonational demands and graphic notation.
Throughout his career Johnston gave thought to how music can convey the concerns of the society in which it was created.
“The fault with most serious composers today, when they undertake to present listeners with an honest view of the tension and complexity of contemporary life,” he wrote in an essay in 1963, “is that much too often they leave it at that.
“Music which evades the issues of complexity and tension or which simply reflects these aspects of life is not accepting its psychological responsibility,” he continued. “The truly significant task for contemporary music is to make this complexity intelligible.”
This article originally appeared in The New York Times.