Channeling equal parts Tom Jones and Barry Manilow, Al Pacino gives an impressive performance in the sweet but shallow "Danny Collins" (rated R) about a rock star who hasn't written a song in decades but can still sell out a stadium. Everything shifts when Collins is given a letter he was supposed to receive in 1971 from John Lennon and Yoko Ono, who urged him to value art over fame. So begins the soul-searching. Collins plans to write new music and maybe even begin a relationship with the adult son he's never bothered to meet. The supporting cast, including Bobby Cannavale and Jennifer Garner, offers memorable performances, too.