Paul Sperry, a tenor who championed little-known American art song and spiky contemporary works, and was praised for his incisive performances of the classics, died on June 13 in Manhattan. He was 90.

His death, in a hospital, was caused by heart failure, his son Ethan said.

In a discipline where his peers tended to stick to tried-and-true German and French classics from the 19th and 20th centuries, Mr. Sperry carved out a niche, singing songs by living composers from his own country. But he also took on some of the most difficult late-20th-century Europeans, like Karlheinz Stockhausen and Hans Werner Henze, who had been shunned by many singers. That boldness earned him steady work, his son recalled.

Mr. Sperry, a Harvard Business School graduate who eschewed a career in real estate and turned to singing, his first love, in his late 20s, was a low-key performer who consistently earned high marks from music critics over three decades. They cited his intelligent approach to song, his understanding of texts, and his imaginative programs.

“Paul Sperry is a true connoisseur’s singer — he may not have the most glamorous tenor voice imaginable, but he does some wonderful things with it, and his programing is always interesting and exploratory,” the critic Peter G. Davis wrote in The New York Times in 1975 about a recital of lieder, including by little-known 18th century composers who preceded Schubert.

When critics found fault with his voice — Mr. Sperry was most comfortable in deeper registers — they still praised the intellect and musicianship behind it.

“Further up, the voice turns grainy, gritty and constricted. Even then, his interpretative virtues are so pronounced that it hardly much matters,” the critic John Rockwell wrote in The Times in 1977.

“Those virtues start with a precise musicality in matters of pitch and rhythm, extend to a sensitively intuitive gift for phrasing and continue with a solid linguistic command — 11 languages — and a nice feeling for dramatic sentiment,” Mr. Rockwell added.

Mr. Sperry delighted in performing showy, often Broadway-esque works by little-known composers he was close to, such as Tom Cipullo and Robert Beaser, as well as the mocking, angular works of American classics like the songs of Charles Ives. Critics had high praise for Mr. Sperry’s attention to words; in Francis Poulenc’s song “Montparnasse,” based on the poem by Guillaume Apollinaire, his diction is impeccable and he is alive to the nuances of Apollinaire’s wry surrealism.

But he was most drawn to American music. “Whether I’m singing Theodore Chanler or Richard Hundley, or Paul Bowles, or Arthur Farwell, or what have you, I’m pounding the drum for American music because I think it’s wonderful,” Mr. Sperry told the music critic Bruce Duffie in 1989. “I feel that I’m doing something that I do better than other people — not better than everybody, but it’s where I feel I have something really special to offer.”

Critics overseas also noticed. Writing in Gramophone, the British classical music magazine, in 1981, Edward Greenfield praised Mr. Sperry’s “fine singing” in a recording of his premiere performance of Leonard Bernstein’s “Dybbuk” suite. There were many other premieres throughout his career, many of them American works, including “Canti del Sole” by Bernard Rands, which won the Pulitzer Prize for music in 1984. Henze, Bruno Maderna, William Bolcom were among the leading composers who wrote for him.

Mr. Sperry also had a full career as an educator, teaching American song and the 19th- and 20th-century song repertoire at the Juilliard School and the Manhattan School of Music. “Paul was very special to me,” Dawn Upshaw, the celebrated American soprano, wrote in a note to Mr. Sperry’s son after his death. “A mentor and an inspiration in my early professional life.”

Mr. Sperry had little patience for complaints, either from listeners or performers, about the difficulties of contemporary music. “What young singers are really saying when they say that is that they don’t want to work that hard!” he told the music critic Richard Dyer of The Boston Globe in 1992. “It does take time and effort, and sometimes the music is not well written — usually I can tell if a piece isn’t well written because I can’t tell if I’m off, and the composer can’t either!”

Paul John Sperry was born on April 14, 1934, in Chicago to Leonard Sperry, a successful businessman who contributed to the development of the Xerox machine, and Rose (Adler) Sperry. He attended the Putney School in Vermont, graduated from Harvard College in 1956 with a degree in psychology, and from Harvard Business School in 1959 with an M.B.A.

Mr. Sperry studied French civilization at the Sorbonne and took singing lessons with the renowned French baritone Pierre Bernac, Poulenc’s partner, in Paris. They remained close until Mr. Bernac’s death in 1979. Mr. Sperry made his New York recital debut at Alice Tully Hall in 1969.

Mr. Sperry would go on to sing all over the world, make numerous recordings, including of Schubert’s “Winterreise,” which his son said he considered the summit of song, and to compile and edit eight books of American song.

In addition to his son Ethan, Mr. Sperry is survived by two more sons, Raphael and Joshua; a brother, Leonard; a sister, Deborah Goldyne; and seven grandchildren. His wife, the sculptor Ann Sperry, died in 2008.

“If my dad had had his way he would have been the great American lieder singer, but nobody wanted that,” Ethan Sperry recalled. “He fell into American contemporary music and that was the best thing that ever happened to him. He kept on saying, ‘I love Schubert, but I never get to talk to him.’”