Both Deniece Williams and Jeffrey Osborne have gone far beyond being anonymous voices on hit records. A complementary double-bill, Williams, a former backup vocalist for Stevie Wonder, and Osborne, who had a string of hits as L.T.D.'s lead singer, proved their command of the stage last night at Constitution Hall.

Sleek and slinky in a red-sequined tunic and slit harem pants, hair flashing with red glitter, Williams was a hybrid of Minnie Ripperton and Aretha Franklin. Her splendid gospel-trained voice took off like a rocket, leaping octaves in ear-splitting squeals, scooping out guttural growls and shudders. She tended to overdo the pyrotechnics, however, with too much vocal lace obscuring the satin heart of her melodies.

Osborne was the more dynamic performer, lean and sexy in white pants and open white shirt, strutting and sliding around the stage, punctuating the band's rhythmic punch with body language. His deep, agile voice worked to best effect on the lovely ballad "On the Wings of Love." An emotional duet with his look-alike, sound-alike brother brought the audience to its feet midsong.

The singers shared the same 10-piece ensemble, which faithfully reproduced the studio sheen of their recordings. Osborne joined Williams on stage, taking the Johnny Mathis part of a theatrical duet in "Too Much, Too Little, Too Late."