Perched on a pair of broad shoulders, a cigarette-slim teen-ager, collar up and cap cocked sideways, bobs above the crush of young bodies thumping and bumping to the drummer's beat. On stage, a go-go girl leads the group in a wildly escalating chant for more. The band keeps pumping and a blue haze dances overhead to a medley of funk and soul.

At the foot of the Capital Centre stage, behind a heavy rope and a string of bouncers, the impresario looks quizzical.

"Kids like it," he shouts over screaming horns and a thudding bass guitar, "but it ain't music."

No matter. William (Bill) Washington knows what sells.

Washington is the top promoter of black-oriented concerts in the Washington area and many cities along the East Coast, having parlayed a flair for hoopla and hype and a talent for wheelin' and dealin' into a multimillion dollar enterprise called Dimensions Unlimited Inc.

Run by a staff of five from an office on Capitol Hill, Washington's company regularly fills the Capital Centre and DAR Constitution Hall with star-studded shows such as the Back-to-School Boogie and Cavalcade of Stars. He stages about 200 concerts a year throughout the country; two to four a month in the Washington area.

Some of the nation's hottest pop, rock and soul acts have performed locally in Dimensions Unlimited productions that attract young and old, black and white. Among the performers: Stephanie Mills, The Commodores, Teddy Pendergrass, The Jacksons, Santana, B. B. King, Joan Baez and Aretha Franklin.

Earlier this month, the company brought Sarah Vaughan and Kool and the Gang here for shows at Constitution Hall. In coming months, Dimensions will bring in Ramsey Lewis, The Whispers and Dionne Warwick and will reunite David Ruffin and Eddie Kendricks in a show with The Temptations.

Along the way to becoming a big-league promoter in the glittering world of entertainment, Washington regularly puts his reputation on the line.

"He's honest and straightforward," said WKYS-FM DJ Donnie Simpson who emcees many Dimensions Unlimited concerts. "He's very capable; everything is always organized."

In fact, Washington says he believes that a good reputation is his best business asset. "My word is very important to me. A lot of times all you have is your word."

Washington, however, has his detractors in the concert business, some of whom have been competitors or who have clashed with him in business dealings. But they declined to be quoted by name or provide details of their problems with Washington.

Washington shrugs off any criticism and says:

"I've never stiffed an act, never bounced a check, never not paid my bills."

Beyond the criticism and the praise, Washington's success story reflects this city's love of the All-Night Party, the Big Bash, the Hot Ticket. This year, Washington and Dimensions Unlimited, in the words of local radio ads, will celebrate "10 Years of Solid Gold Entertainment."

In a sense, Washington has come as far as some of the acts he now books. In 1972, he lost money on a Stevie Wonder concert when the singer was in a professional lull. The same year, he promoted a concert featuring Earth, Wind and Fire and paid the nine-man group $2,000. These days, they get $100,000 for a performance.

Washington, 40, grew up in Clarkesville, Va., where, he says, "if you weren't a teacher, preacher or owned a funeral home, you were a farmer." He broke the hometown tradition when he studied physics at Virginia State College and moved to the District in the 1960s where he worked as a mechanical engineer for seven years, including a stint at the National Aeronautics and Space Administration.

Washington said he always wanted his own business so he formed Dimensions Unlimited, unsure whether it would become a parking lot management company, a security service or an engineering company.

In the meantime, Washington organized fund-raisers for Channing Phillips' unsuccessful 1970 campaign for the D.C. congressional delegate seat. He contracted with local bands, arranged dances and sold tickets. By 1972, he had learned a lot about entertainment, quit his $19,000-a-year engineering job and embarked on his first major concert. The first show that he promoted, with Donny Hathaway and Les McCann, filled Constitution Hall.

"At that point I forgot about parking," Washington says, reflecting on how he stumbled into the concert business. "I got lost, I didn't know where to go. I just made a right turn."

Since then, Washington has moved from an apartment on 13th Street NW to a detached, brick colonial home in Upper Northwest. He and his wife Beatrice, who have no children, traded in their Volkswagen and Pontiac for two Mercedes, a sports car and a sedan.

His success is the result of an innovative marketing strategy as well as a sharp business sense. In 1973, Washington made concert history with the 12-hour Dimensions Unlimited Freedom Festival (DUFF) that drew 55,000 to RFK Stadium and netted approximately $200,000. Prior to that, similar all-day, all-star festival concerts like upstate New York's Woodstock had lost money. In 1974, he repeated the successful formula with DUFF II.

Washington said he is always looking for new talent and helping develop young performers is one way to do it.

In the past year, Washington had added young stand-up comics to his concerts as opening acts with the hope that someday they will be able to draw ticket buyers on their own. He is also helping to develop local bands like Rare Essence, Experience Unlimited and Trouble Funk by featuring them in a show at the Capital Centre in June.

In a fast-paced world of deals and sharp negotiations, Washington seems an unlikely player. His manner is anything but flamboyant and he avoids publicity. His eyes are hidden by thick tinted lenses and his face framed by muttonchop sideburns. He speaks rapidly, with a slight stutter and a hint of a Southern accent.

In a tan Ultrasuede jacket, neatly pressed jeans and a wide-collared shirt buttoned to the top, he is unassuming while making backstage deals. Backstage at one of his concerts, a band wants extra performance time, even though a long-running show costs money. "I bet they get their 45 minutes," a staffer says. They do.

For Washington, there have been some sour notes in concert promoting. In 1977, during Federal Communication Commission hearings into allegations of corruption in the soul/rock music industry, Washington testified that he was forced to pay $14,000 to several WOL disc jockeys to keep them from sabotaging a 1974 concert by not playing the performers' records. Washington also testified that a WOL DJ threatened not to play the records of other big name acts to get them to sign with the DJs' own promotion company. The DJs denied the allegations. They said they believed that Washington and others were trying to hurt some of their competitors.

The FCC, as yet, has made no finding in the matter. The DJs are no longer with the station, their promotion company was dismantled and the station, WOL, is now under new ownership. .

Currently, Dimensions Unlimited and Cellar Door Productions dominate the area concert industry. Tiger Flower Productions, a local firm known for promoting shows that it claims are "not just another concert, but an event," has a smaller share of the concert market.

Even despite competitors, the concert dollar is becoming more difficult to grab, Washington say. He says the problems of concert-goers hit by inflation and unemployment are his own. "My biggest competitor is the economy," he said.

His recent Mid-March Jamboree at the Capital Centre featuring the Bar-Kays, Skyy, and Rare Essence lost $30,000, Washington said, and a New Year's Festival at the Capital Centre lost $40,000. Five of his last 10 shows in the Washington area have ended up in the red, he said.

The son of a Pentecostal preacher, Washington jokingly says his next big promotion campaign will include a lot of prayer. And despite the successes, money and glamor of the promotion business, he said, "I just want to work quietly behind the scenes, do my job and make a living."