The success of the musical comedy "The Wiz" is based entirely on its comedy, not its music.

The music is undistinguished and badly amplified, to the point that words are lost because of echoes from the singers' bodymikes. But we already have a wealth of Wizard of Oz songs from the Judy Garland film - "Somewhere Over the Rainbow," "Follow the Yellow Brick Road," "We're Off to See the Wizard" and so on.

What the black version of Dorothy's odyssey has to offer is contemporary humor, both oral and visual. And entirely different, but excellent, interpretations of the Oz characters who have just about passed into American folklore: the pluckly Dorothy, the Scarecrow without a brain, the Tin Woodsman without a heart, and the Lion without courage.

Beyond the topical jokes - calling Emerald City "The Green Apple" and even referring to 14th and U Streets, a location no doubt varied as the road company moves on - the humor is from its modern tone. What the Wizard likes about his position is "the simple things in life - power, prestige and money." When Dorothy pleads "You gotta help me get back to Kansas," he replies, "I dont't gotta do anything," and she obediently rephrases the request.

Rich comedy is also supplied by Geoffrey Holder's direction and costumes, similar to but more successful than what he did in "Timbuktu!," the black version of "Kismet." That had a stunning bird dance; this has an equally stunning monkey dance with Lewis Whitlock and a chorus of climbing, shrieking monkeys. This has, also, Holder's bright, extravagant, exotic costumes and busy staging.

Dorothy is played by 18-year-old Renee Harries, with her bosom ill concealed by building up the whole area above the waist. Her optimistic energy is delightful and her piping voice both funny and winning. On the only other emotion required of the part, fleeting fear, she is weaker.

Her three companions on the Yellow Brick Road, however, have each created a characterization as perfect in its way as the quite different ones of Bert Lahr, Ray Bolger and Jack Haley. Charles Valentino's Scarecrow is amazingly boneless; Ben Harney's Tinman metal-spirited; and Ken Prymus' Lion a feline combination of fur and fury.