The National Chamber Orchestra opened its brief Summer String Institute concert series Monday night in the F. Scott Fitzgerald Theatre in Rockville with an imaginative program that ranged in style from the exuberant, moody romanticism of Brahms's Op. 8 piano trio to the playful, jazz-influenced first movement of Paul Schoenfield's aptly titled "Cafe Music."

The NCO Piano Trio, which gave the concert, includes three of the Washington area's finest chamber musicians: violinist Jody Gatwood, concertmaster of the NCO; Lori Barnet, the orchestra's principal cellist; and pianist Edward Newman. Their performance was given primarily as an object lesson for the middle and high school string players participating in the institute, but it also attracted an enthusiastic public audience. For both young musicians and adult music-lovers, the trio gave an exemplary demonstration of technical precision and emotional responsiveness.

The players established a high standard in the Brahms Trio, composed in his youth and extensively revised in his maturity. Playing with tight coordination, the trio probed every facet of the music: long, limpid melody with dramatic interruptions in the first movement; rhythmic bounce in the second; soulful meditations in the third, with an audaciously slow tempo that worked beautifully, contrasting with the fast second and fourth movements.

Washington composer Herman Berlinski was represented by his variations on one of Felix Mendelssohn's last songs: "Allnaechtlich im Traum seh' ich dich" ("All Night I See You in My Dreams"). Commissioned for a premiere in Leipzig on the 150th anniversary of Mendelssohn's death, the work is imbued with a melancholy sense not only of that loss but of the outrages perpetrated against his work and his memory during the Nazi era. Its moods change rapidly with each beautifully crafted variation: wistful, angry, sentimental--above all, dramatic.

Ernest Bloch's Three Nocturnes inspired the players to heights of gentle lyricism and emotional intensity. Schoenfield's Allegro concluded the evening joyously with a series of thematic transformations on a tune closely related to "Ain't She Sweet" in many pop styles. Schoenfield has said that he intended "to write a kind of high-class dinner music which could be played at a restaurant but might also (just barely) find its way into a concert hall." He succeeded.