Randolph Peter Best cuts an unassuming figure onstage. Wearing a white moustache, a frizzled taft of white hair, a boyish grin and drooping eyes, today he looks more like a retired auto mechanic than a former Beatle. Still, watching him perform at a tiny music club in a suburb of Santiago, Chile, one couldn’t help being moved by his affection for live music, the apparent zeal with which he plays the drums, and his almost-embarrassed response to the crowd’s adulation. His humility makes it clear that he is no rock star, which is a big reason why Pete Best is so easy to like…