The two toughest tickets to secure on the Sundance Film Festival's opening weekend were a concert featuring Dave Grohl with an army of guests and the Saturday night world premiere of the documentary "History of the Eagles, Part One."

High-profile film festivals, generally speaking, do not program two documentaries in such prime positions. But Grohl's "Sound City" and the Eagles provided a level of cachet as film and live experiences that others in the competition may not have delivered. The pictures have credibility with the film crowd-Grohl's directorial debut, "Sound City," boasts a cinematographer, editor and writer with lengthy documentary credits; "Eagles" had an Academy Award winner in producer Alex Gibney whose previous work focused on weighty contemporary issues.

Unlike scores of other competition films, "Sound City" and "Eagles" knew where they were headed post-Sundance, the festival's primary role being a launching pad. Grohl's concert, with Stevie Nicks, John Fogerty, Rick Springfield, Foo Fighters and others, dominated the first 24-hour news cycle after opening night and alerted the world that there's a documentary about a recording studio that opens Jan. 31 and goes online a day later.

The Eagles-Glenn Frey, Don Henley, Joe Walsh and Timothy B. Schmit-flew into Park City, Utah, for a rare press conference where Showtime confirmed that it would be airing "Part One" and "Part Two" on Feb. 15 and 16. Henley told the audience after the premiere that a disc of eight performances from 1977 will be part of a three-disc DVD set. Its release could come as early as March 19, but the Eagles have stopped short of announcing a date.

For his part, Grohl says, "Don't know much about film festivals but Sundance represents something that is parallel to 'Sound City'--it's away from the glamour and glitz, it's about like-minded people getting together who do their projects in small groups and then gather to celebrate them. We made sure we would be ready even though there were no guarantees we would get in. I can't imagine doing this in Cannes."

Sundance has become a prime starting point for documentaries, a fact born out the last two years by "Senna" in 2011 and last year's "Searching for Sugar Man," now an Oscar nominee.

Two films showed up at this year's Sundance without distribution but with musicians in tow to elicit attention. "Twenty Feet From Stardom," which sold domestically to Radius/the Weinstein Co. on the first night and to international sales company Wild Bunch three days later, was the focus of the Sundance Institute's concert as the film's Darlene Love, Merry Clayton, Lisa Fischer, Tata Vega and Judith Hill performed. Stars of "Muscle Shoals"-Percy Sledge, Dan Penn, Spooner Oldham, the Swampers and others associated with the Alabama recording scene-performed at BMI's SnowBall. The film was still unsold as of Jan. 22.

"Stardom" director Morgan Neville says that to "independent filmmakers, the underdogs in the business, and a film like ours, which is about underdogs, it's a perfect launching pad," referring to Sundance, which screened his film on opening night. "It's the Super Bowl of the documentary world."

Neville's film has the necessary ingredients to become a hit. It tells a story of people that mainstream audiences are unfamiliar with, but the people they worked with--Michael Jackson, the Rolling Stones, Ray Charles, Motown stars--are legends. The music is familiar. It's "Gimme Shelter" and "Sweet Home Alabama," "He's a Rebel" and "Lean on Me."

The narrative arc is compelling and each singer, trampled on and discarded, has his or her own level of redemption. Add to that the high-profile talking heads--Bruce Springsteen, Stevie Wonder, Mick Jagger, Sting--that enhances the story and, one has to believe, the singers will participate in whatever road show accompanies the film.

"Muscle Shoals," directed by Greg Camalier, is a strong documentary too, but more specialized as it concentrates on geography, race, music and the Faulkner-like life of FAME studio owner Rick Hall. With a late-date premiere, its debut could easily be lost in the announcements of winners and closing-weekend ceremonies.