It is mainly as a recitalist that British pianist Leslie Howard has built up a local following in recent years and, bad weather notwithstanding, they were out in force to hear him Tuesday at the Museum of Fine Arts. This time, however, in the role of chamber performer on a Nova concert that coupled him with a number of Utah Symphony players in music of Mozart, Mendelssohn, Lutoslawski and Dohnanyi.

And with the exception of the Lutoslawski, his "Epitaph" for oboe and piano, number is the word, as Mozart was represented by a quintet, the K. 452 for piano and winds, and the other two by sextets, lending an almost orchestral air to the evening.Mozart himself was the pianist for the premiere of the K. 452 Quintet, in 1784, proclaiming it "the best thing I have written so far in my life." By the same token I doubt he would have found much to quarrel with in Howard's keyboard stylings, always animated and always in balance. Otherwise this performance profited from some attractive wind playing, particularly from oboist James Hall and bassoonist Mitchell Morrison (both of whom did justice to the trilling figures of the slow movement), but sometimes seemed a trifle deliberate and just a little bit square.

That did not diminish the force of the opening movement, however, or one's pleasure at hearing the concluding Rondo taken not Allegro moderato (as it is sometimes marked) but as a real Allegretto.

Even more compelling was the Mendelssohn, his early Sextet in D major for piano and strings, whose finale, marked Allegro vivace, was here taken at a breathtaking clip for a mercurial finish. The result was that the strings were occasionally left behind; nor, earlier, were they always well blended or of uniform pitch. But given the heart and soul of their playing, and Howard's virtuosic account of the piano part - which at times he really let fly - there was no denying the music's vitality, often prefiguring the Octet, or the depth of the writing, with its interesting emphasis on the lower voices, consisting of two violas, cello and bass.

Against this the Lutoslawski offered a brief 20th-century respite, its starkly contrasted, free-form modernism showcasing Hall's firm shaping of the oboe line, with the piano generally highlighting the music's spikier elements.

After which came a return to romanticism via the Dohnanyi Sextet, a basically Brahmsian essay whose occasionally melancholic character was subsumed in a richly intoned, almost Straussian reading.

I have no problem with that when it serves, as it did here, to bring out the piece's more distinctive qualities, particularly the novel harmonies of the middle movements and the parodistic Viennese episodes of the finale, here properly humorous. But at the same time it also called attention to its occasionally overblown quality and a lack of subtlety in some of the playing (e.g., the horn). On the other hand the fragrant third movement, with its scampery Presto, found clarinetist Edward Cabarga at his best, and even amid the impassioned unease of the first movement Howard's playing was notable for its fluency and restraint.

Upcoming Nova programs are scheduled Feb. 25, April 22 (moved from April 15, to avoid a conflict with the English Chamber Orchestra) and May 13. For information call 537-7019.