Soundtracks often suffer from their heavy reliance on a visual context; remove that and you’re left with anything from awkward segues to a schizophrenic mess. But music is at the heart of PBS’s recent documentary, The Appalachians, which may help explain why the accompanying disc hangs together so well.

Its cohesion is impressive, considering that the songs span nearly a century and include everything from bluegrass, gospel, and Irish folk to blues, jazz, and Western swing. If the idea was to demonstrate how eclectic influences have coalesced and that the tradition is rich and ongoing, the producers have succeeded. Jimmie Rodgers’s “Waiting for a Train” and the Carter Family’s “Wildwood Flower” sit so comfortably alongside contemporary efforts by Jeff Black, Ricky Skaggs, and Jason Ringenberg that a newcomer might not guess which tracks are recent.

The disc evokes the full range of the genre’s preoccupations—from murder to redemption, from poverty to faded love—while showcasing both major artists and some that ought to be. Highlights include June Carter Cash’s “The Road to Kaintuck,” with a vocal assist by husband Johnny. “Electricity,” an upbeat call-and-response by Lambchop’s Paul Burch; and Maggie Hammons’s unsettling a cappella reading of the traditional “When This World Comes to an End.”