Tonight, the place to be, musically, is the Library of Congress--just as last night it was the Barns of Wolf Trap. The primary reason for this imperative is a brightly colored, rhythmically attractive, jazz-flavored piece of music for clarinet, violin and piano called the "Kent" Trio, which was played last night in Northern Virginia and will be repeated tonight on Capitol Hill.

Composed by Walter Watson 15 years ago and not played much since then, the "Kent" Trio managed to steal the show last night on a program that included music of Beethoven and Dvorak. It will be the only piece repeated tonight, when the Library of Congress Summer Chamber Festival moves into the Library, and it has an excellent chance of stealing the show this time from Hindemith and Brahms.

Last night's program, featuring eight of the 12 young artists who will play in this summer's festival, put its emphasis on light-hearted melody, light-footed rhythms and folk or popular flavors. Neither Beethoven's Serenade in D for flute, violin and viola nor Dvorak's Piano Quartet in E-flat, Op. 87 ranks among these composer's greatest or most familiar works. But they are instantly enjoyable in a decent performance and they were a pure delight in the hands of such performers as flutist Pamina Blum, pianist Maureen Wallis and violinist Junko Ohtsu. To surpass them, the "Kent" Trio, for which clarinetist Loren Kitt joined Wallis and Ohtsu, had to be both strikingly original and immediately appealing. It was.

All of the performers tackled the music with an obvious delight, which the audience readily shared. Their playing was precise without ever lacking spontaneity, and they engaged in musical dialogue with an instinctive rapport that was a delight to behold and did wonders for the music. The warmth and clarity of sound in the Barns always makes music there a special treat, but seldom has the place been the scene of music-making that more clearly deserves this kind of sound. For this series, Wolf Trap is offering a free snack (very rich pastry, coffee and ice cream) with each ticket. That was also delicious, but last night the music was the real dessert.