John Sayles invents a rural legend with Honeydripper, based on facts of living black in 1950 Alabama, gingerly exaggerated so that we wish this yarn were true. Like the roadhouse blues Sayles celebrates, the movie has a repetitive, chugging pace getting more infectious by the minute.

The Honeydripper is a shanty nightclub deep in cotton country, owned by piano man “Pinetop” Purvis (Danny Glover is top form) but perhaps not for long. Business is bad because Pinetop sticks to roots blues that can’t compete with a jukebox joint down the road. Creditors want their money, the liquor supplier refuses to advance its hooch and a bigoted sheriff (Stacy Keach) pops in at all the wrong times.

Pinetop plans one big weekend score, bowing to new tastes by hiring Guitar Sam and his new-fangled electric sound from New Orleans. When Sam doesn’t arrive by train, Pinetop and his bouncer Maceo (Charles S. Dutton) devise a scheme involving shoddy electrical wiring, some lying and a drifter named Sonny (Gary Clark, Jr.), who claims to pick a guitar pretty well himself.

The era and plot allows Sayles to do what his best films always do: dig so deeply into the fabric of a culture that it feels as if he always lived there. There isn’t a more trenchant movie about the modern Florida experience than Sunshine State, or Texas tradition than Lone Star, or South American morality than Casa de los Babys and Men with Guns. This time Sayles seems like a crawfishing good ol’ boy, not a kid from Schenectady, N.Y.

Sayles adores this peeled-paint atmosphere, the itinerant gentility of its citizens and the revival vibe of gospel tents and juke joints. Racism is evident but these people have learned to live with it, thriving by turning the other cheek before times when that wouldn’t happen anymore. Honeydripper never preaches but always teaches about African-American perseverance before the protests.

As usual, Sayles devotes plenty of time to peripheral characters, embellishing the film’s spirit, including Pinetop’s ambitious daughter China Doll (Yaya DeCosta), and his wife Delilah (Lisa Gay Hamilton) who is finding religion. The rivalry between a slickster (Sean Patrick Thomas) and a hulking cotton picker (Daryl Edwards) becomes key to the climax. And I love bluesman Keb’ Mo’ as a blind street musician with an ethereal vibe.

Honeydripper gets distracted by a few needless elements – Mary Steenburgen’s privileged wife for example – but Sayles pulls everything else together for a wonderful finale. This is a small movie you can dance to, and the Beach Theatre where it is opening Feb. 8 probably wouldn’t mind.