For goodness’ sake, don’t allow Ian Merrill Peakes to get his hands on that proverbial phone book, because he just might be tempted to wring compelling drama out of a list of random names and numbers. Urge him instead to stick to the juicier role he’s undertaking now at Folger Theatre, where the play is “Amadeus” and the actor’s performance as Antonio Salieri is, well, gorgeous.

The production overseen by director Richard Clifford earns that adjective, too, most especially for the sumptuous costumes by Mariah Anzaldo Hale that imbue the Folger stage with the glittering accoutrements of an 18th-century runway. Tony Cisek’s set — a forest of violin strings, delineating the rich Viennese musical milieu — evokes the thoughtful labors that have gone into all aspects of this revival, one of Folger’s best.

With Peakes as the repulsive yet captivating court composer who, with Iago’s guile, coaxes his brilliant better, Wolfgang Amadeus Mozart, into an early grave, we’re in the very best hands. The high acting standard extends to the other major roles, particularly Samuel Adams’s juvenile-genius Mozart and Lilli Hokama as his radiantly loyal wife, Constanze Weber. Amanda Bailey and Louis Butelli, as Salieri’s corrosive acolytes, add aptly affected sourness to the proceedings, and John Taylor Phillips as Emperor Joseph II neatly accomplishes the comic illusion of a king who’d just as soon be watching an ultimate fighting championship as a Mozart opera.

In “Amadeus,” playwright Peter Shaffer had in mind a poignant consideration of the great injustice of God and art: Why are some chosen for immortal gifts and other questing creative souls consigned to the dustbin of banality? “The patron saint of mediocrity,” Salieri calls himself at the end of a long life spent chasing acclaim, only to die knowing that the work of the prodigy he schemed to destroy would live on and that his would vanish.

“Long” is actually a fitting descriptor for the nearly three-hour “Amadeus,” a play with an illustrious pedigree. Ian McKellen played Salieri when it debuted on Broadway in 1980; Paul Scofield portrayed him in the London production; and F. Murray Abraham won an Oscar for the role in Milos Forman’s 1984 film, which garnered a total of eight, including best picture. Shaffer wrote in an epic manner, as he did for “Equus,” another play about a man transfixed by the obsessive passion of a younger person; there is a grandeur in his style, but it verges at times on the ponderous. In his ongoing colloquy with God, for instance, Salieri intones the same sentiments at least five times. The excesses have one yearning for an editor — or maybe just for fewer words and more music.

For “Amadeus” is also a rhapsodic musical biography, recounted by a guilty bystander. Some of the loveliest interludes revolve around Salieri’s accounts of the glories of Mozart’s innovative operas such as “The Marriage of Figaro,” “Don Giovanni” and “The Magic Flute,” which departed in theme and texture from the stentorian work of the period. (One of the humanizing facets of Salieri is his recognition of his conceited rival’s artistic superiority.) You get tantalizing snippets of the works, courtesy of sound designer Sharath Patel. And while Salieri’s plaintive prayers seem intended as spoken arias — “Let your sound enter me,” he implores. “Let me be your conduit” — the briefest playbacks of Mozart’s music figuratively drown him out.

It matters not a whit, Shaffer tells us, whether Mozart is a colossal jackass given to lewd displays, ridiculous pastel wigs and a hyena’s laugh. Genius, from the spectator’s or listener’s point of view, always gets a pass. Adams, in the tradition of such previous owners of the role as Tim Curry and Tom Hulce, captures the character’s combination of innocence and arrogance. That duality is reflected giddily in the early scene in which he sits at a keyboard and humiliates Salieri with a heavenly variation on the prosaic march the older maestro has written in his honor. Salieri is all labored contrivance; Mozart exuberant effortlessness.

Clifford has conspired with Hokama to make Constanze splendidly complex. She’s a real partner for Mozart, indulging his silliness but never permitting him to turn her into a joke. What a pleasure to see this character given such dimensionality — to be able to grasp fully her tragedy as well as her instinct for survival.

This is, though, Salieri’s play and, on this evening, Peakes’s. What is it about an actor built for heroic effort? Not for playing heroes, necessarily, but for gathering audiences up and taking us into their confidences — and never making us feel they’ve stayed too long? Even in a play that holds that out as a distinct possibility?

Peakes possesses something like his own personal open-door policy: A theatergoer is given full access to his character’s consciousness — and without ever feeling certain what thought or action will come next. That’s the riddle of real talent. One that Salieri never manages to crack.

Amadeus, by Peter Shaffer. Directed by Richard Clifford. Set, Tony Cisek; costumes, Mariah Anzaldo Hale; lighting, Max Doolittle; sound, Sharath Patel. With Yvonne Paretzky, Ned Read, Deidra LaWan Starnes, Kathryn Zoerb and Justin Adams. About 2 hours 55 minutes. $42-$85. Through Dec. 22 at Folger Theatre, 201 E. Capitol St. SE. 202-544-7077.

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