A sure sign of summer's arrival, the annual Herndon Festival is a combination county fair, multi-block party and musical smorgasbord that always offers a few safe choices and the occasional delightful surprise.

On Saturday evening, both ends of that musical spectrum engage in direct competition. On the Municipal Center Stage at 8 p.m., you can catch the return of the Association, one of the smoothest pop acts of the 1960s, responsible for such wedding ballad classics as "Cherish" and "Never My Love," as well as such catchy tracks as "Windy" and "Along Comes Mary." Depending on your level of affection for nostalgia and how well the original members of the group have weathered the years, this could be a lot of fun -- or a painful reminder that there's no going back.

For those seeking something more contemporary, the Depot Stage will host Matt Nathanson, a singer-songwriter whose CDs are full of sensitive, bruised romance but who also exhibits a cheerfully perverse sense of good humor onstage. Talking from his home base in San Francisco, Nathanson immediately hatched a plot when he heard that his 7:30 p.m. start time will give him a jump on the other guys. "I've got a half-hour to play every Association song," he said. "If I could just get their set list before they go on."

Don't put it past him. The tireless road veteran has clocked hundreds of live shows. As a headliner at clubs and show opener for such acts as John Mayer, Train, O.A.R. and Maroon 5, his self-deprecating jokes and shaggy-dog stories charm the crowds.

Nathanson is also up to the challenge of facing a large audience that may not know his music, despite five independent CDs and a recent major-label release, "Beneath These Fireworks" (Universal Records).

"This will be the first or second show I play with a band, which is a neat change for me," he said. Nathanson has previously toured with just one other player, on cello, no less. "The band can catch their attention, but then I'll hopefully be able to hook them in."

Despite the sad tone in many of his songs, Nathanson projected an unflappable joy about his current lot in life -- married, making music and meeting people whose names he used to read in the liner notes of albums. He calls himself "a music geek, a total nerd. Every aspect -- who engineered what record when." And he refuses to be jaded, not even when one of his songs ("Loud") was picked to play during key moments on an episode of "Dawson's Creek."

"Their target market is, like, a 13-year-old girl, and I'm pretty sure that's me. I watched it over and over."

You can get a preview of the Matt Nathanson experience by visiting www.mattnathanson.com, which, according to his press materials, receives literally a million hits a month. "I think I should put in Ben & Jerry's pop-up ads," he said.

The full schedule of Herndon Festival performers is available at www.town.herndon.va.us/festival/. Besides Nathanson and the Association, Saturday offers many hard choices, primarily between tasty alternative rock (Shane Hines Band, Carbondale and Lucky Town) on the Municipal Center Stage and fine local folk (including Lisa Moscatiello and Dave Chappell, We're About 9 and Shane Hines, in an earlier, solo set) on the Cafe Stage.

If you've still got the energy to get your groove on, Sunday offers a 4 p.m. performance by regional jam band heroes Virginia Coalition, as well as small-stage appearances by rising folk star Leah Morgan and the jazz-pop trio Cerulean Groove.

And Thursday and Saturday nights are capped with fireworks. Party on, Herndon!

-- MARIANNE MEYER

The Herndon Festival offers live entertainment on three stages, food, carnival rides and games, children's entertainment and art activities, a business exposition, 10K and 5K races and an arts and crafts show that includes fine arts. Admission is free; tickets for carnival rides may be purchased on-site. Shuttle buses will provide transportation to and from parking locations at the Worldgate Shopping Centre and Herndon High School. For more information, visit the Web site or call 703-435-6868.

Singer-songwriter Matt Nathanson is scheduled to perform Saturday night.