In the early ’60s, The Four Seasons formed the bridge between The Rat Pack and The Beach Boys, retrofitting corner-stoop doo-wop harmonies and supper-club classiness for the rock ‘n’ roll era. And Frankie Valli was their streetwise Sinatra, blessed with an astonishing vocal range that could dip from a helium-high falsetto to a soulful rasp on teen-pop touchstones like “Big Girls Don’t Cry” and “Walk Like a Man,” where he playfully explored the tension between masculine concerns and feminine expression. But the New Jersey–born Valli and his bandmates also showed future boy-band sensations how to evolve beyond pop novelty, embracing proto-psychedelic fuzz on 1965’s “Let’s Hang On,” and, on Valli’s 1967 solo smash “Can’t Take My Eyes Off You,” sophisticated, brass-blasted serenades. And for all their vocal prowess, Valli and The Four Seasons always emphasized robust, Motown-worthy rhythms, allowing the band to seamlessly transition into a suave disco outfit on ’70s gems like “December, 1963 (Oh, What a Night)” and Valli’s silken-grooved theme song for the film Grease. In the mid-’00s, the jukebox musical Jersey Boys fostered a renewed appreciation for the musical depth and daring that made Valli and The Four Seasons so much more than just harmonious hitmakers.