"The Tempest," one of Shakespeare's last plays, is set in a fantasy world where magic resolves and explains almost everything, and the light of reality is softened by a scrim of gauze. "We are such stuff as dreams are made on," says Prospero to his son-in-law, "and our little life is rounded with a sleep."

The Folger Theatre's production, which opened Monday, is only partially lodged in the clouds; too much of it plods firmly on earth. It is too fanciful a play to live in the serious surrounding director Roger Hendricks Simon has provided, and the vocal weakness of many in the company is particularly evident in a play where control is the key to magic.

It starts off promisingly with a storm created with noise, wind and unsteady actors miming the upheavals of an angry sea. Prospero, once the Duke of Milan before his brother treacherously usurped his office, rules a lonely island, on which he landed 12 years before, after being dispatched in a boat so rotten "the very rats instinctively had quit it." He lives there with his beautiful daughter and two spirit-slaves, the benevolent Ariel and the mean Caliban. Prospero has magical powers and locates on his personal radar a ship that just happens to be carrying his enemies, his brother and the king of Naples.

He sends Ariel to create the storm, and later to cast a love spell on the king's son Ferdinand and his daughter Miranda. During the rest of the play the two groups--the shipwrecked bad guys and Prospero and his magic spirits--circle each other until they finally meet and resolve all. Meanwhile Caliban plots with a drunken butler and the jester Trinculo to wrest control of the island from Prospero.

Joseph Wiseman's thoughtful Prospero is a kindly scholar, angular in a quilted robe, sort of a Chinese elder. His performance is high-minded, an honorable grandee who lacks a bit of the mischievousness that might be expected of such a magical personage. Charles Turner's Caliban is a caged animal, raging sullenly at a master who does not appear to be cruel. Turner has chosen to play the role bent over--Caliban is supposed to be "deformed"--but he looks arthritic. Paul Anderson is a sweet king of Naples, and Herb Davis an excellently verbose Gonzalo. Chip Bolcik does well with the thankless role of Ferdinand, making him into a Ken-doll of a character, a sort of dumb blond.

The real treat of the evening is David Cromwell's Trinculo, a gentle clown who lets the playfulness of the role shine through with giddy delight. He is well-assisted by Jim Beard as a broadly drunk butler; the two make an effective combination.

Alas for too many others. Liane Langland's Miranda is totally conventional; she is lovely but dull. The supporting characters seem self-conscious and stiff, intimidated by the language. Russell Metheny's burlap-fringed set is an effective use of the stage, but Bary Allen Odom, whose costumes are usually quite stunning, has clothed the spirits in fluff-decked body stockings that look messy rather than fantastical.

THE TEMPEST, by William Shakespeare. Directed by Roger Hendricks Simon; designed by Russell Metheny; costumes by Bary Allen Odom; lighting by Richard Winkler; choreography by Virginia Freeman; music by John Webber.

With Joseph Wiseman, Paul Anderson, Terry Hinz, Gregory Roberts, Chip Bolcik, Herb Davis, Dylan Baker, Tim O'Hare, Charles Turner, David Cromwell, Jim Beard, Liane Langland, Michael Nostrand, Celeste Morrow, Ann Gelston, Felisa Kazen, Maureen McGinnis, Tracy Flint, Kim Merrill, Kathleen Weber, John Webber, Skip Guidry and Thomas Allen. At the Folger Theatre through April 25.