An article in Monday's Style section about the East Thirteenth Street Band incorrectly identified the writer and composer of the song "Matzos and Watermelon." He is Howard Brofsky.

The irreverent modern artist Larry Rivers achieved the unexpected again Saturday night. He came to the Hirshhorn -- not for an exhibit of his paintings, but to play saxophone with his jazz band.

An art critic might have called it "Action Music," monumentalizing impulse and chance, after the artistic movement called "Action Painting," which characterizes some of Rivers' work. A music critic might have found it closer to a jam session than a performance. But few critics appeared to be present. Most people in the capacity audience of 270 clapped at the solos, laughed at the jokes and asked the Artist for his autograph afterward.

And Rivers, comfortable in the art world, found the "sophisticated" crowd endearing. "I enjoy this audience better than a nightclub."

The band, which formed five years ago, just cut its first album, "The East Thirteenth Street Band." Rivers said that playing saxophone in the band, which rehearses once or twice a week, does not take much time away from his artwork, especially since he lives quietly. "If you are not out doing drugs and running around with women, you have a lot of time left over."

Rivers, who has paintings in the collections of most major modern art museums, brought the group down from New York to kick off the 20th-anniversary celebration of the Smithsonian Resident Associates.

The band opened with Rivers' arrangement of "Blue Moon" and went on to such golden oldies as "Georgia on My Mind" and "All of Me," as well as a kitschy composition by drummer Earl Williams called "Matzos and Watermelon," which supposedly contained elements of funk and "My Yiddishe Mamma."

The musicians, as jazz players should be, were cool. Trumpeter Howard Brofsky, Cinderella-esque in a floor-length white dress, attracted attention at the champagne-and-strawberries reception after the performance.

"It's a long white gown," someone said.

"I thought it was a caftan," said someone else.

"It's a gandurah," said an unembarrassed Brofsky, a musicologist who purchased the robe while on vacation in Morocco. "It's very cool, that's the thing."

The band members, most of whom have other professions, don't sweat too much over little mistakes. Unlike competitive professional New York jazz players, they can afford to play a wrong note now and then.

"Getting it right is not that important. What's more important is getting the spirit of it right," said trombonist Howard Kanowitz, a New York painter.

"Rivers is not scuffling, he's not struggling to make a living, so he has a very good time," said Brofsky.

"Some of the others tend to be sort of traditional and he'll say, 'We don't have to do it that way.' He'll just pick up and start to play during someone's solo," Brofsky added.

Rivers is known for breaking the rules. One of his better-known paintings is "The World's Greatest Homosexual," a controversial painting of Napoleon Bonaparte with patches of erasures and rough collage. He did a takeoff of Emanuel Leutze's "Washington Crossing the Delaware," and copied a Rembrandt that had been roughly imprinted on the top of a cigar box.

Saxophonist David Levy, a dean at the Parsons School of Design, said Rivers has an experimental, ad-lib approach to music. "Mixing the media does give you a greater understanding of the improvisational," said Levy, pausing. "Or even the accidental."

"It the band means so much to him," Brofsky said, referring to Rivers. "He's always after us, saying, 'We gotta rehearse.' " The band practices in Rivers' 13th Street loft (hence the band's name), which is permanently equipped with a piano, drum set and bass.

Kanowitz was just describing the rehearsals ("chaos") when Rivers called him, over the heads of well-dressed reception-goers.

"Howard!" Rivers cried. "We have to go to dinner!" Kanowitz started back down to the auditorium.

Levy and pianist Myron Schwartzman, a James Joyce scholar, tinkled on the piano as everyone put their instruments away. Rivers sang along, with the voice of a frog.

"Let's go!" bellowed Rivers, breaking from his soliloquy. The Artist was hungry and wanted to have dinner. The band members picked up their instruments and left.