People started sitting on the grass and benches of Dupont Circle with lunches or cold drinks in hand about 20 minutes before Swing Works launched into its first piece yesterday.

These were the lunch-time regulars at the circle, passersby and new initiates - all waiting for some noontime jazz performed by the 18-piece ensemble made up of musicians who teach or play in pit bands when they're not getting together to perform for fun.

"The concert is going to be cut short today," said host Jeff Anthony, "because some of the guys have to play for a 2 o'clock matinee at the Kennedy Center."

The announcement didn't chase away any listeners. Instead, they looked for shady spots while the band played Thad Jones' "A Child Is Born" in cool, liquid fashion, as refreshing as lemondade or punch.

"I like this kind of music," declared a 50ish man. "I'd like to see more of the big bands come back. They're playing dance music. If you like to hold a girl while you're dancing, this is the music for you. Bring all the big bands back."

Cosponsored by Discount Records and Books and the Musicians Union, the concert was the sixth in a series of Wednesday and Friday jazz events at Dupont Circle in July. Although tomorrow's concert featuring Terry Plumeri's group is scheduled to conclude the series, Anthony said the concert arrangement may be extended through August.

As the band swung crisply into "That Old Black Magic," up walked Jeff Donaldson, art professor at Howard University. "I just happened on this," he said. "This is fabulous - a great way to spend lunchtime."

Rusty Hassan, a jazz announcer at WAMU-FM, agreed. "It's a lot of fun to lie in the grass and listen to music," he remarked.

During the first two compositions, buzz saws competed with saxophones, and jackhammers clashed with trumpets. But by 12:30, when the temperature hit 84 degrees, Swing Works commanded all attention. And even some of the hard-hat workers were stretched out on the grass, eating lunch.