When a crowd gathers on the courthouse lawn in Leesburg for a Sunday evening performance run by the Bluemont Concert Series, the scene is a familiar one -- families bringing blankets to sit on and picnics to munch on while they enjoy the show. It is only after the performance that a stranger to the concert would be aware of an unusual sight.

"Having 800 people on that courthouse lawn, you'd think that would create quite a mess," said Peter Dunning, executive director of the concert series. "But we ask people to pick up their trash, and after the concert the place doesn't look like anybody's been there."

The secret, said Dunning, the only paid member of the nonprofit group now running its third summer series of concerts in Leesburg, lies in "how you present what you're doing and how you explain to people that this is a partnership. We have a partnership with the town and the county, and part of the partnership is the people" who come to the concerts.

In return for taking care of their trash and paying a $1 admission fee, audiences can attend concerts which, without the Bluemont Concert Series, would probably never be held in a small town like Leesburg.

The performers that Peter Dunning and the concert series bring to Loudoun County (and now, in similar programs, to Fauquier, Clarke and Frederick counties) are a diverse mix -- from internationally known English concertina player Alastair Anderson to Trapezoid, a West Virginia folk and bluegrass group, to lutenist Howard Bass, who has performed at the White House and with Anderson in England and on the back porch in Bluemont, where he lived when he and Dunning first organized the Bluemont concert series.

It was about 10 years ago that a group of friends -- many of whom had just moved to Bluemont from Ohio or New York or somewhere else far from the hills of the Blue Ridge -- began getting together once in a while to play music. They began holding country dances as well, in the old Bluemont school. The word spread, the audiences grew and somewhere along the line a little organization crept into the informal gathering.

"Probably in 1978 we started calling it something," said Dunning.

Now the Bluemont Concert Series has about 800 members who give annual contributions that make up a good part of the group's budget. Last year Dunning and the BCS Board of Directors, with the help of volunteers, presented more than 140 performances in Loudoun County and the surrounding area.

In addition to the summer series and other concerts the rest of the year at the old Bluemont school, the organization brings benefit performances to local hospitals and nursing homes. The Bluemont Concert Series also runs an Artist in Education Program, and last year held 65 concerts in the classrooms of local schools.

Dunning manages the group's growing list of activities on a budget (1983's was $60,000) that represents the "spirit of cooperation" he says characterizes the programs. In Loudoun County, the concert series receives a small grant from the county government and office space in a county building. Leesburg town council annually provides $2,500 for the series, donates use of the courthouse lawn and closes off several main streets to keep the concert area quiet. The Virginia Commission for the Arts provides a small matching grant.

Although some of the performers normally charge up to $2,000 a concert -- more than the Bluemont Concert Series could afford -- Dunning is able to bring them to Virginia by arranging a number of performances in the area during a group's weekend visit. Also, said Dunning, with most of the groups "we have some sort of relationship . . . and they understand we are not a big promoting organization."

For most of the musicians, playing for the Bluemont Concert Series is a "real different sort of experience," Dunning said. Reports from the musicians themselves attest to this, as does the 18-inch high stack of letters Dunning has received from musicians who want to participate.

Greg Artzner of Magpie, which will be in Leesburg this Sunday evening for a 7 p.m. concert of classical jazz and country tunes from the 1920s and '30s, has high praise for Dunning and the Bluemont Concert Series.

"We love playing all the gigs we've done for Peter," Artzner said. "It's a very accessible thing, not like your bigtime concerts . . . . It's a really great series, and I hope he's able to sustain it and keep it going."

Dunning has every intention that the Bluemont Concert Series continue its work. "The cultural spirit is one measure of the health of a community," he said. "I think that spirit lives the strongest in the community that at least in part creates this itself out of its own resources."