Fifty-six years after Judy Garland, Ray Bolger, Bert Lahr, and Jack Haley first warbled their way to the wicked witch's castle on MGM soundstages, The Wizard of Oz at last has appeared as a properly complete, bona fide ''Original Motion Picture Soundtrack'' recording, including emerald green CD trays and a 48-page booklet that, like the classic film, shifts from black and white to color and back again.
Why the big wash-and-brushup now? Chiefly because (go on, trill it because, because, becaaaaause!) Rhino Records, best known for Top 40 pop compilations, signed a contract with Ted Turner this year to mine the mogul's mother lode of old MGM movies for fresh musical material.
''There was no such thing as a soundtrack album when Oz came out in 1939,'' says associate producer John Fricke, a cabaret singer-turned-full-time author and historian. ''It's almost impossible to conceive now, when things like Pocahontas rule thecharts, but film music, especially background music, once had no value outside the movie itself.''
To rescue Oz's elaborate musical ''underscore,'' adapted by Herbert Stothart from Harold Arlen and E.Y. Harburg's songs, the Rhino restorers had to review hundreds of original takes. Some five hours of this material, first released on a 1993 laserdisc, has been winnowed and compressed for the Rhino set, making it a cinch to savor such gemlike outtakes as Bert Lahr's extended ''If I Were King of the Forest'' riffs (he audibly cracks up his costars) and a track of Garland weeping her way through an ''Over the Rainbow'' reprise, deleted from the castle sequences.
More than anything, Fricke says, the extras in this archival set demonstrate a talent that modern technology has rendered unnecessary. ''Nowadays, pop singers only have to get through two bars at a time,'' says Fricke. ''It's all spliced, double tracked, and nursed along. Except for a few bars, Garland's movie take of 'Over the Rainbow' was sung live in a single go. These people had command.''