FORT WORTH — An exceptional virtuoso, clarinetist Julian Milkis, joined a pianist and a string quartet Saturday afternoon and helped steer the Chamber Music Society of Fort Worth in a new direction.For one thing, he introduced a sound not usually heard on the society’s programs; his instrument’s tones permeated the performance. For another thing, his presence brought into play a whole range of new pieces, including one of Brahms’ greatest compositions. The range of styles was also expanded.The Brahms Clarinet Quintet in B minor is from late in the composer’s career. In fact, he had decided to retire. But hearing the art of clarinetist Richard Muhlfeld inspired him to compose a series of pieces spotlighting the instrument, including the quintet.This is a beautiful work, but also quite melancholy (it’s strange that the two characteristics can coexist, but they often do, in music as in the other arts). Although the sound is strongly flavored by the clarinet, the quintet is not a virtuoso piece with the clarinet accompanied by the strings. The two violins, viola and cello have much to say.Milkis’ sound flowed beautifully, and strongly where required. His partners — violinists Gary Levinson and Felix Olschofka, violist Richard Young and cellist Brinton Averil Smith — contributed a flowing performance of their own, whose lyrical character was punctuated by occasional dramatic outbursts.This was a rare performance (rare around here) of a great masterpiece.The musical styles were drastically different for the rest of the concert. To start off, pianist Daredjan Baya Kakouberi joined Miklis and Levinson for Trio on the Roof, by Alexander Goldstein. As the title suggests, this is a musical tribute to Fiddler on the Roof. It takes melodies from the musical and plays around with them in various ways. Of the four brief movements, I liked best “From Dawn to Dusk,” whose tricky rhythms and fade-away ending were appealing.At times, the piano seemed a little too loud. It’s a phenomenon I’ve noticed before in the auditorium of the Modern Art Museum. The piano is pushed up close to a wall, magnifying the sound.The same group of musicians played Ballade on Themes From “Porgy and Bess,” an arrangement by Robert Russell Bennett using Gershwin’s Bess You Is My Woman Now and It Ain’t Necessarily So.This was a charming and entertaining bit, as were the other mostly brief works on the first half of the program. They included five pieces for string quartet and clarinet: two arrangements from Gershwin, a work by Eubie Blake, one by Dick Hyman and one by Alexei Shor. Hyman’s Clarinata was a real showpiece for clarinet, impressively played by Miklis and partners. Rendezvous for Clarinet and String Quartet, by Alan Shulman, written for Bennie Goodman, was an interesting interplay of jazz and more sedate styles.