Dominick Argento, a Pulitzer Prize-winning composer who was likely the most celebrated creator of new American operas between the heyday of Gian Carlo Menotti in the 1950s and the advent of Philip Glass in the 1970s, died Feb. 20 at his home in Minneapolis, where he had lived for six decades. He was 91.

His music publisher, Boosey & Hawkes, announced his death. The cause was not disclosed.

Mr. Argento was always a force apart. He belonged to no compositional school, preferring a distinctly eclectic language that appealed both intellectually and emotionally to his audiences. At a time when most of the celebrated American composers were based on either the East or West coasts, where they could work together and help promote one another’s music, Mr. Argento lived and worked in Minneapolis throughout his career, teaching composition at the University of Minnesota and working closely for many years with the director Sir Tyrone Guthrie at what became the Guthrie Theater.

In 1976, Mr. Argento spoke of his passion for the singing voice for ASCAP magazine: “The voice is not just another instrument. It’s the instrument par excellence, the original instrument, a part of the performer rather than an adjunct to him.”

He said that he wanted his work to “communicate, not obfuscate.” He once described himself to High Fidelity magazine as a traditionalist “in the broadest sense.” “I have never had any desire to write music for library shelves. If you want a school, include me in the Mozart, Verdi, Mussorgsky school,” Mr. Argento continued.

In all, he wrote a dozen operas, including “Christopher Sly” (1963), “Postcard from Morocco” (1971), “The Voyage of Edgar Allan Poe” (1976), “Miss Havisham’s Fire” (1979) “Casanova’s Homecoming” (1984) and “The Aspern Papers” (1988). Several of these works have entered the repertory.

When searching for material for his operas, Mr. Argento told The Washington Post in 1990, he looked for “stories where the human condition is in some kind of crisis, where someone is struggling, facing a very difficult emotional situation — even things like madness.”

Reviewing a revival of “Postcard From Morocco” at the Juilliard School in 1985 for the New York Times, I wrote: “Mr. Argento’s idiom is largely tonal, conservative yet distinctly his own, and borrows from ragtime and other strains of popular music. He writes sympathetically for the voice; there are few of the jagged, angular leaps and bounds that so often typify modern opera. He is also a deft parodist — a ballet sequence entitled ‘Souvenirs de Bayreuth’ provides one of the funniest send-ups of Wagner since Emmanuel Chabrier turned ‘Tristan und Isolde’ into a galop for two pianos.”

It was a song cycle called “From the Diary of Virginia Woolf,” a setting of eight entries from Woolf’s diaries, that won Mr. Argento the Pulitzer Prize in 1976. He later said that this was a “piece that, when it was finished, was even better than I’d hoped for.”

The world premiere took place in Minneapolis with the distinguished English mezzo-soprano Janet Baker as the soloist. When asked by High Fidelity how he felt when the work received one of music’s highest honors, he replied: “The Pulitzer Prize? You mean Christmas in May. I did not even know the piece had been submitted.”

Dominick Argento was born Oct. 27, 1927, in York, Pa. His parents were recent Sicilian immigrants who ran an inn and restaurant. He was largely self-taught as a child, listening to musicians who visited the area and reading biographies of composers, including Gershwin and Stravinsky.

After service in the Army in the 1940s, Mr. Argento studied at the Peabody Institute conservatory in Baltimore on the G.I. Bill. His principal teachers at Peabody were Nicolas Nabokov and Hugo Weisgall, the latter of whom introduced him to opera. Mr. Argento graduated in 1951. He later worked with Luigi Dallapiccola in Florence, a city he would grow to love deeply.

Several other widely divergent composers — Howard Hanson, Alan Hovhaness and Henry Cowell among them — nurtured Mr. Argento’s lifelong eclecticism. He received a doctorate in musical composition from the Eastman School of Music in Rochester, N.Y., in 1958.

His first opera, “Sicilian Limes,” a setting of a work by the Italian writer Luigi Pirandello, received its premiere in 1954. Mr. Argento later withdrew it, along with several other works that he considered juvenilia.

A later work, the song cycle “Casa Guidi,” based on writings by Elizabeth Barrett Browning, received a Grammy Award in 2004 for best contemporary classical composition.

Mr. Argento moved to Minneapolis in 1958 to teach at the University of Minnesota and never left for long. He retired from teaching in 1997.

Mr. Argento was married to the soprano Carolyn Baker from 1954 until her death in 2006. During their long years of marriage, the Argentos spent their summers (and sometimes the whole year) in Florence, which they regarded as a second home.

After his wife’s death, Mr. Argento composed a musical tribute, “Evensong: Of Love and ­Angels,” which had its premiere at Washington National Cathedral in March 2008. His wife “is almost a living presence in ‘Evensong,’ ” Minneapolis Star Tribune critic Michael Anthony wrote, “which must count as one of her husband’s most lyrical and radiant compositions.”

Mr. Argento was considered a deeply inspiring teacher, and his students included Libby Larsen and the late Stephen Paulus.

Daron Hagen, another American composer who has worked extensively in opera, wrote a fan letter to Mr. Argento while a teenager growing up in Wisconsin.

“When I sent him my music and asked him for advice, I didn’t really expect him to respond, but he did, with gentle, persuasive wisdom and integrity,” Hagen said Thursday. “His letter ended with an invitation to come to work with him. For Argento was America’s greatest opera composer: Like Verdi, he knew that his every note of lyric theater was subject to revision; he promoted his creative vision without an ounce of personal grandstanding; he was humble personally, and artistically regal, and never, never forgot that opera is about the human voice.”

Page is a professor of music and journalism at the University of Southern California. He won the Pulitzer Prize for his writings about music at The Washington Post.