Autumn arrives, symbolically and astronomically, with the annual Common Ground Country Fair, running Friday through Sunday, Sept. 21 through 23, at the Maine Organic Farmers and Gardeners Association’s Common Ground Education Center off Crosby Brook Road. The MOFGA event celebrates organic country living, so contra dance is de rigueur. This year, though, the rural event will embrace a little city sophistication.

The Midcoast is no stranger to ballroom dancing, especially the swing genre. Belfast had one of the area’s first forays into swing some years back, when Bob and the late Carla Brown brought Harlem-style Lindy Hop to town, and there are classes at the dance studio and regular practice sessions on the east side. Camden and Rockland shared Swing & Sway for a number of years, and now Katie Tranzillo helms an enthusiastic partner dancing crowd at High Mountain Hall. But chrome leather heels are pretty rare at Common Ground Country Fair, where natural fibers are more the rule.

If anything can turn the Maine Folk Traditions Stage into a Fred-and-Ginger venue, it’s the Portland-based State Street Traditional Jazz Band. Formed in 1989 to preserve and perform the old jazz from New Orleans, State Street offers an authentic mix of up-tempo jazz, blues and old spirituals, as performed in the Big Easy from the turn of the 20th century to the 1920s. After that time, jazz began to migrate to Chicago, St. Louis and New York and to diversify into the multiple styles the genre boasts today.

“We play the original rhythms; it’s essentially a form of ragtime, transposed for brass and other instruments,” John Page, band manager, said.

So swing dancing is pretty traditional, after all. The State Street Traditional Jazz Band’s dance sets are on the fair’s first day, at 1 and 4 p.m.

More expected Maine traditions to be enjoyed during the fair include shape note singing, the aforementioned multiple contra dances, lots of strings — the fairgrounds are just half an hour from the Maine Fiddle Camp — and plenty of opportunities to do less structured boogying.

Bands playing the fair include Zulu Leprechauns; Inanna, Sisters in Rhythm; the Gawler Family Band; El Grande; Laurie Jones Band; The Maine Squeeze; Tumbledown Saints; Happy Town and fest-capping T-Acadie.

There are duos galore, including the Oshima Brothers, Lynn Deeves with Robby Coffin, Hilton Park, GoldenOak, Putnam Smith with Seth Yentes, Red Beans & Rice, Old County Road, Rural Roots Revival, Gabriel Zacchai & Rootgrass and Builder of the House. Solo artists include Jud Caswell, Kat Logan, Martin Swinger, Sara Trunzo, Caroline Cotter and more.

The Children’s Area hosts its own lineup of performers; the other music takes place on the Spotlight Stage, in the Amphitheater and on the aforementioned Maine Folk Traditions Stage, where the annual Fiddlers’ Showcase is Sunday at 11 a.m. The full schedule can be perused online at mofga.org/The-Fair and in the big fair tabloid, found around the state and, of course, on the grounds — look for poster contest winner Arika von Edler’s happy sow and piglet on the cover.

Ticket outlets closed earlier this week, but advance tickets are still available online via brownpapertickets.com. And there are good reasons to get them in advance: even with the handling fee, there’s a discount; and through-the-gate time is significantly reduced. Tickets are $10 in advance/$15 at gate; $8/$10 for those older than 64; and free younger than 13, MOFGA members, fair volunteers, persons with disabilities and school groups (Friday only). Those who ride bikes or take the train to fair get $2 off their tickets.

The fair opens each day at 9 a.m.; vendors close down at 6 p.m. Friday and Saturday, 5 p.m. Sunday. Music is just a part of the weekend, which includes everything from equestrian vaulting to the Harry S. Truman Manure Pitch; see the schedule for all the options.