"My heart is wild with fear, my throat is dry," sang tenor David Eisler last night in the Terrace Theater. If the words were true, his voice showed no sign of it, but he had every reason to feel that way. On a night when he expected to be in Toronto, singing Bernstein's "Candide" for the Canadian Opera, he was in Washington singing Stravinsky's "The Rake's Progress," an opera he had learned but never had sung anywhere else.

Eisler was rushed in for the dress rehearsal last Saturday, after tenor Jerry Hadley, who had been cast in the crucial title role of Tom Rakewell, came down with a throat ailment. Eisler has been studying and rehearsing every waking moment since then.

If Martin Feinstein, general director of the company, had not told the audience before the show began, chances are most people would not have noticed it was Eisler's debut in the role. Vocally, he had the role completely mastered. Theatrically, there were sometimes microscopic problems of timing and interaction, little signs of momentary uncertainty or extra caution -- the kind of things that are smoothed out by time, but not in one long weekend. At his worst, though, he did as well as most tenors manage after weeks of rehearsal.

Eisler's voice is clear, light and pleasant in tone; he shapes and projects words with care, and he responds effectively to all the nuances of this role, which range from idealistic love through arrogance to nihilism, despair and finally madness. He has obviously studied the words and music thoroughly (he was Hadley's understudy for the New York City Opera production), though he was unfamiliar with the Washington Opera's staging.

The role of Tom Rakewell carries a substantial part of "The Rake's Progress" (though all of the soloists and a few chorus members have moments of solo glory), and Eisler carried it effectively. The surest sign of his effectiveness was the abundant laughter every time he delivered a comic line. His applause at the end was warm and prolonged.

Before Hadley's illness, the principal roles were expected to be the same as they were in the Washington Opera's first production three years ago, and the new names and faces were all well-chosen. Beverly Evans, as Baba the Turk, has a less prominent role than she had in "The Medium," but she fills it with a fine voice and striking stage presence. Jeffrey Wells brings vocal distinction to the rather neutral role of Trulove, Tom's prospective father-in-law, and Jonathan Green is splendidly flamboyant in the small, colorful role of the auctioneer, Sellem. Baritone Gordon Hawkins has only a few lines as the keeper of the madhouse, but he sings them with rich tone and polished style.

The role of Anne Trulove, like that of Micaela in "Carmen," is a hard one in which to make an impression -- a nice girl almost engulfed in a world of madness, pretension and debauchery. Sheri Greenawald, a memorable Mimi from "La Bohe me," brings this pale role to vivid life, particularly in the later scenes and overwhelmingly in the madhouse finale where she plays Venus to pacify Tom, who thinks he is Adonis.

Charlotte Dixon, repeating the role of Mother Goose the brothel-keeper, was as vivid as she had been three years ago, vocally and theatrically. The chorus, small but excellent as it usually is in the Terrace, played roles that ranged from prostitutes to madmen to a crowd going crazy with greed at an auction.

Next to the role of Tom, the most crucial in the opera is that of Nick Shadow, the devil figure who lures Tom to his destruction, fails to win his soul at the last minute and sinks back into hell in a burst of fury and frustration. William Dansby, repeating the performance he gave three years ago, is the ideal interpreter: oily, malevolent, smoothly persuasive and plausible, and faintly redolent of decay. He was in excellent voice last night, but his chief virtues were theatrical. He never overplays a role in which the temptations are many, but he has a spectacular scene at the end, sinking slowly into an open grave, cursing as he goes, until all that can be seen are his hands, clutching at the edge of the pit and then pulled under.

Conductor Nicholas McGegan invigorates the score much as he did last season in the Washington Opera's production of Handel's "Semele," and he has the orchestra in good form.

As for the opera, it is one of the 20th century's unquestionable masterpieces in this form -- a collaboration of two great artists, Stravinsky and W.H. Auden, working together in perfect harmony. Three years ago, this was one of the Washington Opera's vintage productions. This time around, it is at least as good as before.