Mr. Janis withdrew from the concert stage — temporarily, as it turned out — and devoted himself to songwriting, a pastime of his youth that he had given up when his touring schedule became too demanding.

With the encouragement of the folk singer Judy Collins, he sent a tape of his songs to Warner Chappell, the music publisher, which engaged him to compose 22 songs for a theatrical setting of “The Hunchback of Notre Dame,” with lyrics by Hal Hackady and a book by Anthony Scully. The show had its premiere at the Westbeth Theater, in Manhattan, in 1993.

Also among Mr. Janis’s works was an incidental score for “Cooper and Hemingway: The True Gen,” a 2013 documentary about the relationship between Ernest Hemingway and Mr. Janis’s father-in-law, the actor Gary Cooper. Mr. Janis and Maria Cooper married in 1966. An earlier marriage, to June Dickson Wright, ended in divorce. Mr. Janis had one son, from his first marriage, Stefan, who died in 2017.

In the mid-1990s, Mr. Janis returned to performing, gingerly at first, giving short performances at benefit concerts, at which he shared the bill with other performers, and working his way up to a program of works by Mozart, Schumann, Chopin and Prokofiev for an Alice Tully Hall recital in 1998 that commemorated the 50th anniversary of his Carnegie Hall recital debut.Born Byron Yanks in McKeesport, Pa., on March 24, 1928, he grew up in Pittsburgh, where his father, Samuel, owned a sporting goods store. The elder Mr. Yanks had changed the family name from Yankilevitch before his son was born, and he would change it twice more — to Jannes and, finally, Janis — by 1943.

Mr. Janis’s mother, Hattie, was a homemaker. She first noticed her son’s musical talent when he was given a xylophone, around age 5, and quickly began picking out melodies. When he began correcting mistakes his older sister Thelma made while practicing for her piano lessons, Mr. Janis’s parents allowed him to have lessons of his own.

His first teacher, Abraham Litow, was impressed enough with Mr. Janis to bring him to New York to play for the virtuoso pianists Josef and Rosina Lhevinne. When he was 7, Mr. Janis, accompanied by his mother, moved to New York to study with the Lhevinnes and their assistant, Adele Marcus, at the Chatham Square Music School.