His close friend and fellow painter, Isa Barnett, said Mr. Barnett had been torn between being a painter and a musician when he was young. When he chose to be an artist, he put into his art the same flamboyance, effervescence and love of life that went into his piano playing, Barnett said.
"Whether he was doing dancers in Spain or maskmakers in France, the celebration and the festivity were there," he said.
His lyrical, lively and colorful works are found in some very prestigious places. One of them, The Widow in White, is at the Philadelphia Museum of Art. Others are at George de Braux Galleries in Paris, the Cleveland Museum and the Galerie Internationale in New York, as well as in many private collections.
A series of watercolors of the Western Wall and other scenes from Jerusalem are owned by the Israeli government, which commissioned them.
One of his earliest works - a scene from an opera - hung for years in the hallway at the Furness School in South Philadelphia where he had painted it about 60 years ago, when he was just 12.
Born in Philadelphia, Mr. Barnett graduated from South Philadelphia High School and won a scholarship to the Philadelphia College of Art (now the University of the Arts).
Over the years, he won a Guggenheim Fellowship, the Philadelphia Da Vinci Medal, the Indiana State Drawing Award, the Pennsylvania Academy of Fine Arts Board of Directors' Award and the Dawson Water Color Award.
He had many one-man shows in Philadelphia, New York, San Francisco, Paris and Madrid, and his work sold well, one gallery owner said.
Mr. Barnett was about 5-foot-6 and slight and, with his goatee, dancing blue eyes, long reddish hair and a habit of dressing as if clothing were costume, he was the perfect model of a painter, said Barnett, who regretted never having painted his friend.
For most of his life, he was a realist painter, said Benjamin Mangel, who had a show of Mr. Barnett's work at his Center City gallery in 1988. He painted portraits on commission, still lifes and, often, interior domestic scenes.
In recent years, his work became more emotionally charged, Jennings said, and the style became more expressionistic. During a trip to Spain in 1985, bombs exploded in airports in Rome, Paris and Vienna, and caused him and Jennings to cancel part of their trip.
"He seemed to be very concerned with terrorism," Jennings said, "and we have quite a few canvases dealing with that."
Mr. Barnett taught at the University of the Arts for 18 years and also at the Delaware Art Museum, Fleischer and Long Beach Foundation of the Arts.
When he was younger, he and his former wife, Rita Wolpe Barnett, also a noted artist, ran the Creative School of Arts in the city's Logan section, where he taught children that "it's more important . . . to enjoy painting than to create a great picture," he said at the time.
He tried to get that same message across throughout his teaching career, Barnett said. He did not teach by formula, he said, but by "liberating" students by sharing his enthusiasm for the work.
Besides his companion, Mr. Barnett is survived by three stepchildren, David, Larry and Nicole Jennings; a brother, and a sister.
Services are private.
Contributions in his memory may be made to the University of the Arts, Development Office, 320 S. Broad St., Philadelphia 19102, and directed to the William Barnett Fund.