CHAMBER ENSEMBLES aren't as popular as full orchestras in the classical music world. But Philadelphia's Wister Quartet has spent more than 20 years convincing fans that this more intimate format offers different aural pleasures that are just as worthy.

Four then-members of the Philadelphia Orchestra formed the Wister Quartet in 1987, taking its name from Frances Anne Wister, the chairman of the Women's Committee of the Philadelphia Orchestra from 1910 to the '50s. Nancy Bean and her husband Davyd Booth, first and second violinists respectively, form the quartet alongside violist Pamela Fay and cellist Lloyd Smith.

Chamber ensembles like the Wister Quartet are small by design. They date to the Baroque era, Corelli's and Vivaldi's time, well before the modern full-sized orchestra became the norm. Each instrument has the luxury of playing a distinct melody so each performer's artistry can shine. In a full-size orchestra, individual talents recede into a single collective sound.

Chamber groups are to full orchestras as an intimate coffeehouse band is to the Rolling Stones. A louder and fuller sound is simply more popular; chamber music is seen as something for the purists. Bean has faced this prejudice throughout her career.

"After one of our performances, people come up and say, 'Wow, this isn't what I thought it was going to be!' " Bean said. "Usually people expect to feel unimpressed," which is why Wister strives to present as diverse an array of music as possible at each performance. The group is determined to show that chamber ensembles are as capable and adaptable as a full-sized orchestra.

Nothing exemplifies the Wister's impressive range more than its performance of three drastically different pieces for the string quartet on Sunday at the German Society of Philadelphia, where the quartet does an annual concert series.

Two Impressionist composers, Claude Debussy and Charles Griffes, provide the bulk of the performance's unexpected elements.Joseph Haydn, a German composer from the Classical era, rounds out the repertoire and brings the ensemble back to its roots. "Haydn is there for the German Society, but he is also viewed as the father of the string quartet," Bean noted.

The Griffes piece, "Two Sketches Based on Indian Themes," channels the music of the Chippewa tribe. Native American music, known for drums and improvisation, wouldn't seem to have much in common with a string quartet. "Griffes takes the merest kernel of the Indian music and makes it his own," Bean explained.

And Debussy's "String Quartet" is one of the most popular pieces the group performs. "The Debussy is the most gigantic piece of the program, a tour de force of the string quartet, Debussy at the height of his composing powers," Bean said.

Wister Quartet, German Society of Philadelphia, 611 Spring Garden St., 3-5 p.m. Sunday, $20, 215-627-2332, germansociety.org.

Art Attack, a partnership with Drexel University, is supported by a grant from the Knight/NEA Community Arts Journalism Challenge and administered by the Greater Philadelphia Cultural Alliance.