Neal Zaslaw, flutist, and Anne Chamberlain, pianist, deserved more than the handful of the faithful at Paine Hall last Monday evening. The first Boston performance of John Harbison's "Duo" rewarded the small audience that did show up.

Harbison's five-movement work, placed in the middle of the program, vacillated strangely from the dramatically original to the depressingly banal. In the first movement, "Fanfare," for example, an oom-pah-pah calliope followed an exciting, dissonant flourish. But Harbison nicely exploited the resonance of the piano and the technical facility of the flute.

The quality of the performance fluctuated curiously. At times, in the "Lullaby," for instance, the piano overpowered the flute. Yet in the roaring "Intermezzo," Miss Chamberlain, much as she may have tried, could not be sufficiently brutal.

The program opened and closed with sonatas by Bach and Haydn. Though Mr. Zaslaw's tone initially carried too much breath, it projected the low registers, and the breathiness disappeared later. Miss Chamberlain contributed wrong notes in the difficult spots; in the delicate passages she failed to make the crucial notes sound.

She demonstrated her technical ability, and some musicianship, however, in her solo, Brahms' "Variations on a Theme of Robert Schumann, Op. 9." She brought out the melody from a complex texture, occasionally blurring it with too much pedal.

The performers and Mr. Harbison should have had a bigger audience. Future recitals ought even to enjoy the amenity of having the house lights dimmed during the performance.