You know Ray Parker Jr.’s music even if you don’t immediately recognize his name. The Detroit native penned the indelible smash “Ghostbusters,” the theme song to the 1984 film of the same name. But by then he was already a prolific recording artist and performer, having honed his chops as a session and touring musician with Stevie Wonder and the Rolling Stones while he was still a teenager and writing hits for New Edition, Diana Ross and others. “Who You Gonna Call?” traces his path from the segregated streets of Detroit in the 1960s to the top of the charts and the Hollywood Walk of Fame, offering a candid look at a complicated artist whose musical legacy is overdue for wider appreciation. U.S. premiere.