D. A. Pennebaker virtually created, defined and refined the cinema verite style of the documentary film, so what more natural than finding he and his partners, Nick Doob and Chris Hegedus, at the helm of just such a documentary about the staging of the concert performance of the music from the Coen Brothers’ film, O Brother, Where Art Thou?? It’s even less surprising to find that Pennebaker and company have done the event and its creation proud, unobtrusively crafting a loving portrait of the musicians and the music involved. The approach is simple: follow the performers around and talk with them (or let them talk) while they prepare for the concert and then present the concert. A somewhat more elaborate idea seems to have been considered with an introduction that tries to literally depict Ralph Stanley bringing the music “down from the mountain” to Nashville. As the oft-cited father of bluegrass, this is not unreasonable, but the approach is somewhat at odds with the rest of the film, and the execution of this opening isn’t terribly effective. Once the film gets past this and into the musicians and their music in a more relaxed manner, it hits its stride and never falters, despite the obvious paucity of budget. Shooting on digital video, Pennebaker and his co-directors capture much of the sense of immediacy of the entire affair, and the format itself adds to its pleasantly informal character. There are certain drawbacks to the cinema verite approach, which are part and parcel of its fly-on-the-wall nature. Since it eschews, for the most part, staging events, shies away from question-and-answer interviews, and avoids the use of identification titles, the viewer is left to pick up on who the various participants are only on the evidence of the film. In Down from the Mountain this generally works, but often in an after-the-fact manner. Many viewers may be hard-pressed to tell who many of the performers are during the backstage and rehearsal periods that precede the concert itself, though the bulk of the information is later conveyed in the concert when interlocutor John Hartford introduces the acts. (However, at no time does anyone answer the question of why there are clearly five members in the Fairfield Four!) The performances themselves are letter-perfect and a delight to any admirer of the Coen Brothers’ film. When presented in this fashion, it’s impossible not to realize just how much the essence of O Brother, Where Art Thou? is contained in the music it contains — from the naive pleasures of Hartford’s rendition of “Big Rock Candy Mountain” (its lyrics a shock to anyone who grew up on Burl Ives’ sanitized children’s version) to Ralph Stanley’s unsettling performance of the grim “O Death.” At the center of the film is John Hartford, who was dying of cancer at the time of the film’s making. The effects of the illness, which he only addresses in passing, are especially obvious in his offstage moments, but even here his sweetness and humor are undimmed. When talking about receiving the lyrics for “Big Rock Candy Mountain” by fax machine, he dryly remarks, “There on page two it had a couple verses of tum-tiddy-tum-tiddy-rummy-tum-tum, which I just don’t sing on general principle.” Onstage, however, a kind of transformation takes place, and, though looking frail — almost to the point of appearing ethereal — Hartford, the consummate professional, takes over and delivers one of the most purely charismatic performances I’ve ever seen, single-handedly giving the concert its unifying center. No, it’s not an earth-shattering film, but neither is it meant to be. It is simply a beautifully done record of a very unusual event — and one that inadvertently serves as a testament to John Hartford, making it a very special document of musical history.