One is tempted to use the expression "a cornucopia of delights" in describing Tuesday evening's Nova concert at the Musuem of Fine Arts, its first of the season. Except that might call disproportionate attention to the horn, which was featured in only two selections, the Hindemith Horn Sonata and the Poulenc "Sextour" for piano and winds.

For if there was any one hero on this eclectic program it was probably pianist Jonathan Purvin, who offered strong support not ony in those pieces but also in a group of Mozart songs and Chausson's "Chanson Perpetuelle," each highlighting the artistry of mezzo-soprano Lani Poulson.By the same token hers is a more powerful voice than one is used to hearing in Mozart, at least these songs, most of which tend to be sung by lyric sopranos. The result to my ears was that, for all her musical and textual acuity, she missed some of the elusive sparkle of the Cherubino-like "An Chloe" and "Der Zauberer," whose giddy enchantment seemed a mite calculated. But the darker emotions of the "Trennungslied" ("Parting Song") and "Abendempfindung" - perhaps the composer's masterpiece in this form - proved right up her alley, as did the mini-drama of Luise sending her lover's letters up in smoke ("Al Luise die Briefe").

Likewise her work in the "Chanson Perpetuelle," here the version for piano and string quartet, where after sinking easily into both the language and the semi-impressionistic mood, she rose memorably to the climax. Indeed the final "de l'absent" seemed almost torn from her, the instrumental complement dying quietly underneath.

Solo horn in the Hindemith sonata, dating from 1939, was William Barnewitz, who gave this minor masterpiece his all, catching not only its brooding undertones but its "Mathis"-like nobility - e.g., the vigorous climaxes. Throughout his robust tone was well controlled from top to bottom and, as indicated, Purvin emerged as a more-than-equal partner, particularly in the finale.

Persichetti's Serenade No. 6 for Trombone, Viola and Cello (1950) is for an even more unusual combination, something taken advantage of here by trombonist Larry Zalkind and his violist wife, Roberta. Joined by cellist Ellen Bridger, they projected its occasional quirkiness with everything from plaintiveness to good humor, but always with skill and, where appropriate, an almost subliminal tension.

Tension was likewise evident in the Poulenc Sextet, which came in for a flavorful if occasionally edgy reading. At least that was my reaction to the opening movement, whose energetic outer sections came across as a little harsh. In between, however, one admired Mitchell Morrison's haunting bassoon and, to a lesser extent, Jane Lyman's flute (especially the low register), James Hall's oboe and Edward Cabarga's clarinet.

Further programs are set Jan. 15 (with Australian pianist Leslie Howard), Feb. 25 (with the Western Arts Quartet), April 15 (with violinist Joseph Silverstein) and May 13 (with harpist Konrad Nelson).