Imagine a fanciful construct like both an elaborate sacher torte and a chapel of high rococo decoration. That's "Amadeus," Peter Shaffer's serio-comic historical drama about Wolfgang Amadeus Mozart as seen through the eyes of his envious contemporary, Antonio Salieri.

At one extreme, you have the most chocolaty of treats, darkly luscious, made complex with flavorful layers and topped with whipped cream. At the other, you have a similar playful excess, flung aloft into visual arabesques, mixing golden explosions with rosy curves.

Ted Pappas' elaborate production at the Public Theater honors both. James Noone's gorgeous set is soaring rococo, from its patterned marble floor and boisterously Corinthian columns to a mirrored rear wall of lacy filigree, topped by glittering chandeliers and a cartouche of tumbling cupids. The visual feast is completed by Susan Tsu's equally luscious costumes.

For edible delights, there are the creamy dessert concoctions to which Salieri is addicted, including one intoxication called Nipples of Venus, suggesting the young mistresses he pursues.

But the richer, layered pleasures at the heart of "Amadeus" are in Shaffer's script, alternating between the farcical comedy and engulfing poverty of the boy genius Mozart and the bitchy wit and gnawing nihilism of the vengeful Salieri.

In other words, there's a lot going on.

And the Public production realizes it with great visual and aural panache, not incidentally thanks also to a large and capable cast of 19.

More about that in a minute. But you could also describe "Amadeus" less favorably, as someone once did, as the world's longest record jacket. Disregarding the put-down in that, it does suggest the worthy, Masterpiece Theater/Music Appreciation 101 aspect of the play.

I do mean "worthy." It's fun to feel you're learning something about one of our greatest cultural heroes. Whether or not the play's biographical facts are quite right, and leaving aside the question as to whether the historical Salieri ever really plotted against Mozart in this way, Shaffer brilliantly puts his little lectures on Mozart's musical perfection in the mouth of the man who hates him, making the testimony that much more impressive.

Set in 1781-91, the decade of Mozart's musical genius and personal failure at the Viennese court, the story is told in retrospect by Salieri, on the verge of his own death in 1823. A self-described musical mediocrity, he understands that Mozart's genius marks him as loved of God and hates him for it -- and Him, as well.

It doesn't lessen the interest of the play to note that the story of the sophisticated, dried-out observer obsessed with someone else's passionate, primal instinct is one Shaffer has written several times: "Equus," "Lettice and Lovage," "The Gift of the Gorgon," even "The Royal Hunt of the Sun."

So ultimately, what must raise "Amadeus" above luscious sweet or architectural delight is the torment within Salieri -- the conflict in his soul between aesthetic perception and human passion. And this is the one place I don't think this "Amadeus" pays off.

Salieri is at least half the play, and all the architecture, decoration, wit, music, comedy, learning and other actors, including even Mozart, are the other half. As Salieri, the skilled Tony Abatemarco does mostly heroic work, taking us into his confidence and snapping off campy witticisms as he alternates between smiling courtier and aggrieved Machiavelli. But for all his verbal agility, he never made me shudder. He never found the deeper, stiller chord to touch my heart and make me care.

Abatemarco's considerable skills are well supported by the rest of the cast. As Mozart, Harris Doran is so deliciously childish and arrogant that you almost share Salieri's distaste. As you'd expect from having seen his Emcee in last year's "Cabaret," Doran deftly handles Mozart's turn from ribald comedy to growing despair. Daina Michelle Griffith has a similar breadth in the smaller role of Mozart's canny wife, Constanze, ranging from sexual provocateur to victim.

The rest of the large cast provides varieties of comedy, led by the brilliantly vacuous Emperor of Daniel Krell, all smiling, flailing vapidity. Larry Daggett and Brett Kennedy are suitably venomous as Salieri's informants. As Count Orsini-Rosenberg, Larry John Meyers manages to grow a dozen chins and make his mouth look like a letterbox set in the midst of a pumpkin. Alex Coleman has a high comic haplessness (and finally a sour meanness) as Mozart's patron, Baron van Swieten.

Pappas conducts this almost operatic play with great command. It's a scrumptious construct. But if it is like a glittering rococo chapel, it's one where knowledge of God, however implicit in the divine strains of Mozart, is missing from the tragedy of Salieri. Call it a chapel tourists may visit for edification and pleasure, not transport.