Verdi described his first version of "Simon Boccanegra" as "monotonous and cold." Even with the extensive revisions that came years later, this opera -- which the Metropolitan Opera performed at the Kennedy Center last night -- needs a powerful performance to bring it alive.

With Sherrill Milnes in the title role, which utterly dominates the work, there was power aplenty.

Boccanegra really was the doge in 14th-century Genoa, and this opera traces the two decades of his reign, ending in the dramatic death scene of Simon, poisoned by his enemies. Milnes, with his commanding physical stature and his magnificent baritone voice, pulled off the death of Simon smashingly -- literally, even, as he fell flat to the floor at the end.

This part is a vehicle for the kind of heroic baritone that Milnes is. There's a whole range of vocal sonorities -- from those huge, wonderfully resonant, musical tirades, to some beautifully soft high notes, as at the end of his moving duet with his daughter, Amelia.

The latter role also was memorably performed, by little known soprano Aprile Millo, who made her Met debut only a few months ago. Hers is a fresh, warm voice -- not too large, and a bit in the Victoria de los Angeles mold. Pitch is dead center and vocal color is even from top to bottom. She also is a good actress.

The vocal sound of the opera is overwhelmingly dark, with two roles each for baritone and bass. The big bass part, Jacopo Fiesco, was sung by the eminent bass Paul Plishka, that frequent vocal partner of Milnes. Their duet in the last act was one of the high points of the evening.

Baritone Richard J. Clark was strong and sonorous as Paolo. And tenor Vasile Moldoveanu, whose voice is small by comparison with all these deep voices, sang with suitable style.

This production, which was borrowed from the Chicago Lyric Opera because Milnes wanted the Met to do a "Simon," is pretty minimal. One would have expected something more imaginative from Tito Capobianco.

"Simon" moves slowly, mainly because most of its music is quite deliberate. And conductor Nello Santi did little to add any pulse.

This sense of lassitude was considerably aggravated by the hot house temperature in the theater during much of the evening. The air conditioning went out for what seemed like more than an hour, as it did in the other Kennedy Center halls as well. A spokesman said there were "mechanical difficulities."