After more than a decade of crafting songs and careers for other artists, songwriting duo Nickolas Ashford and Valerie Simpson are making a strong bid for stardom in their own right.

At Constitution Hall last night, they turned out one of the most polished and upbeat pop performances of the year. They descended on stage from a stylized, art deco Chrysler building, all lavender sequins and fringe, and sparkled all evening.

Both were hard-working entertainers, playing right into the audience, teasing and cheerleading. If Simpson plays the sassy sex kitten, Ashford is her equal, hamming up his leonine image.

Acting out their "Private Lives" in concert, they played the melodramatic love couple role to the hilt, trading smoldering gazes and stalking each other. Songs like "Street Corner" and "High-Rise" are love songs for grown-ups, effortlessly catchy poperettas about the perils and pleasures of urban romance.

Ashford's gravelly falsetto and Simpson's silky soprano blend happily. Their orchestra, led by session man Ray Chew, reproduced the lush sound of their elegant R&B records. The show climaxed with "Still Such a Thing," a new romantic anthem as defiant as their "Ain't No Mountain High Enough."

Opening was local favorite Nona Hendryx and Propaganda. She seemed to be broadening her style, mixing in buoyant pop while hanging on to her aggressive rock/funk experiments.