Spanning eras as easily as he does octaves, Frankie Valli has led the vocal group The Four Seasons since the early '60s, inspiring the smash musical Jersey Boys. His skyscraping falsetto steals the show on hand-clapping bubblegum zingers like “Big Girls Don't Cry” and “Walk Like a Man”. The group's frisky, layered delivery powered many other chart-toppers, but there's more to Valli than dizzying high notes. He drops to a dreamy croon for the smouldering solo ballad “Can't Take My Eyes Off You”, and The Four Seasons proved just as adaptable on 1975's celebratory “December, 1963 (Oh, What a Night)”, a spot-on overture to disco.