It’s not the authentic cadence of folk and rock in the context of Southern California, or even the thinly veiled nods to drugs (“Strange Young Girls,” for example), that made The Mamas & The Papas’ happy-hippie stance seen so ironic yet timeless. It was John Phillips’ clever songwriting, arranging, and production that did it: he was a true ’60s pop genius, second only to Brian Wilson. Proof is here, in this essential set that collects the band’s four ’60s albums. Nearly every song and harmony haunts, from the beguiling “California Dreaming” to the pop-eerie “Twelve Thirty (Young Girls Are Going to the Canyon).”