George Walker, 96, a pianist and Pulitzer Prize-winning composer trained in Philadelphia whose melancholy but warmly reassuring Lyric for Strings became a popular calling card, died Aug. 23  in Montclair, N.J., his family told NPR.

Mr. Walker blazed a trail in the overwhelmingly white world of classical music. He achieved a number of African American firsts: the first to win the Pulitzer Prize in composition, among the first to graduate from the Curtis Institute of Music, and the first African American instrumentalist to solo with the Philadelphia Orchestra.

Listeners praised the Walker style as economical and finely crafted.

His work is "modern and fresh-sounding — and is both lyrical and complex at the same time," said composer David Ludwig, artistic adviser to the president at Curtis. Mr. Walker, he said, echoed Bartók "in his preternatural gifts as a performer, sophistication as a composer, and his commitment to spirituals and American folk musical traditions."

His scores received new attention after he won the 1996 Pulitzer for Lilacs, which had been commissioned by the Boston Symphony Orchestra.

As a pianist, he was "really and truly a major talent," former Curtis director Gary Graffman once said. In 1945, Mr. Walker recalled, he was the first African American instrumentalist to solo with the Philadelphia Orchestra, playing Rachmaninoff's Piano Concerto No. 3 conducted by Eugene Ormandy after winning the orchestra's student competition.

But Mr. Walker said that the year after his piano debut he went backstage after a rehearsal to request an appointment with Ormandy to show the conductor his new Lyric for Strings.

"He said he didn't have time," Mr. Walker told the Inquirer in 1996.

It was 45 years more before the orchestra programmed the six-minute work — on its first tribute concert for the Rev. Dr. Martin Luther King Jr. in 1991.

"I'm not bitter," he said, "but what I would like to say is, Why has it taken so long for the Philadelphia Orchestra to recognize what pretty much everyone else accepts?"

Lyric for Strings was played on two more of the orchestra's MLK concerts, and made its subscription-series debut in 2006. The orchestra also played Lilacs and his Violin Concerto in 2009 with son Gregory Walker as soloist.

Curtis played a pivotal role in his development. There, he studied piano with Rudolf Serkin and composition with Rosario Scalero. Efrem Zimbalist, the school's director, arranged a town hall recital debut. He was in the Curtis Common Room one day when another Serkin student, Seymour Lipkin, told him he was conducting a radio concert with string orchestra. Mr. Walker suggested adding a double bass part to a string quartet he had just written and expanding the work for string orchestra.

"Of course I knew Barber had done that [with his Adagio for Strings], but I never talked about it in front of anybody else. It was just right on the spot," Mr. Walker told an interviewer from the site NewMusicBox. "And he said yes. So I rushed home and put the parts together and gave it to him and they played it."

And Lyric for Strings was launched.

In May, Curtis awarded him its president's alumni award at commencement — the school gave him an honorary doctorate in 1997 — and its orchestra performed Lyric in Verizon Hall in April with a smiling Mr. Walker in attendance.

George Theophilus Walker, who lived in Montclair, was born in Washington. His father came to the U.S. from Jamaica and became a physician after graduating from Temple University. His mother bought him a piano and his first music books.

"The same respect for Mozart and Bach that we heard at church carried over at home," he told the Inquirer. "Our piano teacher taught the same things we would have gotten at the Juilliard preparatory department. It was a different world. There was culture. All the boys who were my friends studied either piano or violin and we were expected to take it seriously."

He earned degrees from Curtis, Oberlin College, and Eastman School of Music; was a Fulbright fellow; and studied with famed pedagogue Nadia Boulanger. He was the second African American to graduate from Curtis, in 1945 (another pianist, Russell Johnson, graduated in 1928), and was the first African American to receive a doctorate from Eastman, in 1956, a spokesperson for that school said. He taught widely over the decades, at the Peabody Institute, Rutgers, the University of Delaware, and Smith College.

Mr. Walker's compositional style encompassed considerable range. Lilacs for voice and orchestra is both disturbing and stirring. His Piano Sonata No. 3 is terse and rather dry.

"He used different techniques at different times," said pianist Leon Bates, who commissioned the Piano Sonata No. 3 from Mr. Walker in 1976 after hearing his music for the first time played by his Temple University professor Natalie Hinderas. "I don't think there was a sense of him moving forward on a gradual path out of one style into another. I think he tended to go back and use ideas as he wanted to."

But it was the quintessential American sound of Lyric for Strings that made its composer an American classic.

It embodies "a lyricism unique to the tradition of the many storied composition graduates of the Curtis Institute of Music," said Philadelphia Orchestra assistant principal double bassist Joseph Conyers, who conducted the piece in Italian cathedrals on a 2015 tour by Philadelphia's All City Orchestra. "There's an arch in the piece that begins with an optimism embodied in love and compassion. That love morphs into an acknowledgment of the struggle that such positive forces can face in the world — a world where optimism can seem in short supply. Ultimately, hope wins out, and the listener is left both content and comforted."

In addition to his son Gregory, he is survived by another son, playwright Ian Walker.