The sun always seems to be shining whenever a Monkees song is playing. Here are their brightest, most buoyant moments, including the jangly guitars and mop-topped harmonies of “Last Train to Clarksville” and “Pleasant Valley Sunday,” the plaintive piano and Davy Jones’ wistful vocals on lovelorn ballad “Daydream Believer,” and the woozy psychedelia of “Porpoise Song,” from their trippy 1968 movie, Head.