When Bono and Mick Jagger are two of the least colorful and relevant talkers in a rock ’n’ roll documentary, you know the filmmakers have struck gold.

In “Muscle Shoals” — about a small Alabama town that played a mammoth, almost mystical role in 20th-century American music — the platinum recordings made there in two landmark studios are lined up like a hall of giants, from Aretha Franklin’s “Respect” and Percy Sledge’s “When a Man Loves a Woman” to the Rolling Stones’ “Brown Sugar” and Lynyrd Skynyrd’s “Free Bird.”

The classic albums recorded there (see also: Bob Dylan, Wilson Pickett, Etta James, Paul Simon, Allman Brothers, Ray Charles, Willie Nelson) are only part of what makes the story so impressive. This richly layered documentary also champions the city and local musicians who blueprinted the so-called Muscle Shoals Sound, where everything from American Indian lore and Southern grit to determination and plain old luck are cited for explaining how the place became an unlikely musical hotbed.

That it’s a podunk town nowhere near New York or Los Angeles adds to the fascination (the Stones hanging out at the local Holiday Inn in 1969 is among the enjoyable archive footage). And then there’s the fact that most of its session players were white dudes backing pioneering African-American singers in the shadow of Gov. George Wallace’s “segregation forever” speech.

“It always seems to come out of the river [and] the mud,” Bono pontificates in true Bono Maximus fashion, drawing a parallel between the messiness of the Mississippi, Mersey and Tennessee rivers in becoming musical ground zeroes. Through tall tales and rich cinematography, “Muscle Shoals” provides a sense of place greater than any GPS.

The story gets unexpectedly muddy, too. It centers on FAME Studio operator Rick Hall, whose personal life reads like a Southern tragedy from William Faulkner.

Adding to Hall’s misery, the musicians who worked for him (including bassist David Hood, father of Drive-by Truckers leader Patterson Hood) launched the rival Muscle Shoals Studio once FAME became famous. The tragic deaths of Duane Allman and half the Skynyrd crew also play into the film.

Of course, from all that drama and discourse and dirt-coated character rose some of the most ascendant, spiritually rousing music of the rock era. Even fans who don’t know Muscle Shoals by name know its music by heart. Now they can also see how much soul went into it.