You could be forgiven for assuming that Lambert and Stamp are some

You could be forgiven for assuming that Lambert and Stamp are some forgotten folk-rock duo of the Peter & Gordon variety. Kit Lambert and Chris Stamp were part of London’s ’60s rock scene, though not as performers but as managers, promoters, producers, and mentors. They helped transform a mod-favorite club band called The High Numbers into The Who, nurtured the songwriting talents of Pete Townsend, and supported the band until its breakthrough.

They are a colorful pair with an interesting story. Lambert, the posh, Oxford-educated son of a classical-music conductor, and Stamp, a working-class bloke and younger brother of Terence Stamp, were aspiring filmmakers when they met as assistants at Shepperton Studios. They bonded over their shared passion during the age of the French nouvelle vague and hatched a plan to break into the movies: They’d mold a raw, young rock-’n’-roll act into a success, chronicling the odyssey on film. The Who was merely a means to an end, an irony that gets lost in the familiar showbiz arc here: early enthusiasm and creative energy, breakthrough success with Tommy, and the inevitable falling-out over success, money, and control.

The best of these showbiz docs provide a window into an era or a cultural moment, and director James D. Cooper delivers at first. He works the mod style, swinging London attitude, and jump-cut editing to capture both the period and the passion of this odd couple as they bluff their way through the music industry on instinct and impulse. Then that social backdrop is lost as the film dives into the finer points of creative conflicts and lawsuits. For committed Who-ologists, Lambert & Stamp mostly sidesteps the disagreement as to how much influence the duo really had on the band’s music in general and Tommy in particular.

Kit Lambert died in 1981, the second band casualty (after Keith Moon) of excess and addiction. Stamp, who died in 2012, lived long enough to tell Cooper his story and repair relations with Townsend and Roger Daltrey (who are also interviewed). I fear this doc is just a little too inside-baseball for anyone but fans of The Who and British music of the ’60s. It’s a good story, though not strong enough to frame the entire decade.

LAMBERT & STAMP Opens Fri., May 8 at Sundance Cinemas. Rated R. 117 minutes.