The Beatles’ rooftop concert in Let It Be prefigures This Is Spinal Tap (inset). The Beatles rooftop concert in ‘Let It Be’ is a template for every great band reunion moment — and possibly every romcom — to come. Forty-five years ago, the Beatles were kaput, having called it quits in a flurry of torts and acrimony. A final studio album, “Abbey Road,” meant to show them as a functioning unit in 1969, was overtaken by “Let It Be,” recorded earlier but released later as a documentary and album, awash in Phil Spector strings and choirs. (It still won an Oscar for Best Song.) The documentary is one of life’s painful reminders that people — even Beatles — grow tired of one another. Directed by Michael Lindsay-Hogg, Let It Be takes us behind the scenes as John, Paul, George and Ringo — but mostly Paul — try to pull an album together out of general ennui. At this point in time, after the death of manager Brian Epstein, the end of touring, John’s recent infatuation with Yoko Ono and George’s commitment to spiritual detachment, there were few cheerleaders left in the Beatles. Paul, the task-driven Gemini, still fit the bill, and he is the one that takes up the reins on this project. Lindsay-Hogg’s camera dotes on Paul. He’s there in the opening in a tight shot, vamping some Bach-like inventions on piano (just so you know he’s the “serious” musical Beatle); Paul also gets loving close-ups singing Let It Read More …