The Kennedy Center Handel Festival ended its seventh season Saturday night with a rarity, the opera "Xerxes," or "Serse," as it is known in Italian. It was given in a concert version at the Concert Hall.

"Xerxes" is a bit of an anomaly. It includes what is probably the single best-known excerpt from the many Italian operas that Handel composed for the London stage--the aria "Ombra mai fu " or, as generations of aspirant pianists have come to know it, the "Largo from 'Xerxes.' "

The Largo is over before the performers are six minutes into the more than three-hour score, though, and what follows is relatively unfamiliar even to the experienced opera listener.

"Xerxes" is said to be Handel's only comic opera. That label seems to rest more on the technicality that the characters don't pile up dead at the end than that it is a monument of humor. Based on Saturday's performance, the listener should be prepared for a few amusing antics, but should not expect to be convulsed with laughter. If "Xerxes" is meant as parody of old Baroque conventions, that dimension was not clear in the Handel Festival's performance, but since the performance was not staged, perhaps that is understandable.

The story itself, which is derived from Herodotus, is rendered so silly that as a drama the opera would be compelling only as a parody. There is Xerxes, the king of Persia, who is played by a coloratura mezzo-soprano. He is carried away with Romilda, the young daughter of a captain in his army, who in turn is in love with the king's brother, Arsamene, who is also played by a soprano (there are only two male roles in this opera, and they are not major ones).

What redeems all of this is the music. There is, of course, the Largo (which, astonishingly enough, is not an emotional tribute to a person, but to "my beloved plane-tree"). Other high points: an extraordinarily poignant duet between Arsamene and Romilda near the end of the third act (it sounds almost Mozartean); a mighty aria by Xerxes soon after that, "Crude furie degl' orrido abissi," and Romilda's grand aria, "Chi cede al furore," which ends the second act.

The voices were good, but not in the blockbuster category for which Handel apparently wrote. Mariana Paunova got off to a shaky start in the title role, but kept getting better as the evening progressed. The same was true of Hilda Harris as Arsamene. Linda Mabbs, as Romilda, was strong from beginning to end. The sisters Katherine and Kristine Ciesinski were fine as Amastre and Atalanta. John Ostendorf and Richard Dirksen were both splendid as Elviro and Ariodate.

Stephen Simon's conducting was fluent and understated, and Norman Scribner's chorus was excellent.