Reprinted from yesterday's late editions.

Question: What is more absurd than an opera whose hero is schlepped onstage by a big white swan?

Answer: An opera whose hero is schlepped onstage by a big invisible swan.

I think the swan in Thursday night's performance of "Lohengrin" at Wolf Trap must have been named Harvey. At least, like the famous rabbit of that name, it was invisible to the audience, though apparently visible to the hero.

Outside of the missing swan, and the way the canvas walls of Elsa'a (presumably stone) castle billowed in the wind, the Metropolitan Opera's production of "Lohengrin" Thursday night was generally satisfactory. There were occasional moments with small imperfections, and the chorus and orchestra, superbly conducted by James Levine, made a more consistently strong impression than the solo singers.

At the opera's beginning, the bad guys, Mignon Dunn as Ortrud and Morley Meredith as Telramund, seemed to have a considerable vocal edge on the good guys - Lucine Amara as Elsa and John Alexander as Lohengrin. Amara's voice has served the Metropolitan well in a variety of roles for a quarter century, and is still highly serviceable, though perhaps less thrilling than it once was.

A large part of this opera's perennial appeal (and also a major reason for its excessive length) is its wealth of slow-moving medieval pomp and pageantry. Wagner's stately music makes the length almost justifiable, but a strong stage picture is also needed for the eye, if the opera is to work on all levels. Ming Cho Lee's stage sets, adapted for travel, were uneven in their effect but generally striking costumes and the fine stage direction of Phebe Berkowitz, they were effective.

At its best, this production approached the finest in the international operatic circles, at least visually; and if it did not quite match the Bolshoi's "Boris" or La Scala's "La Boheme" for sheer elaboration and telling details, if made at least credible effort.