One of the most successful pop vocalists of the 1960s and 1970s, Frankie Valli's athletic voice, which could rise from a muscular tenor to a stratospheric falsetto with pinpoint accuracy, was the signature sound for dozens of chart-topping hits by the New Jersey-based vocal group the Four Seasons. From 1962 through 1968, Valli, childhood friends Tommy De Vito and Nick Massi, and teenage prodigy Bob Gaudio provided sleek, street-smart and altogether danceable hits like "Sherry," "Big Girls Don't Cry," "Dawn (Go Away)" and "Let's Hang On!" that for many listeners, were key colors in the tapestry of their teenaged years. Valli later established himself as a solo artist with the brassy "Can't Take My Eyes Off of You," and balanced his own music career with various versions of the Four Seasons. In 1975, he struck gold in the disco era with a string of hits, including "December 1963 (Oh, What a Night)" and the theme to "Grease" (1978). His vast body of work kept him in the public eye as a nostalgia act throughout the 1990s and early 2000s until proper respect was paid to his life and accomplishments with "Jersey Boys," a wildly popular and award-winning musical. The production, which sprung up around the globe to universal acclaim, underscored Valli's enduring contributions to popular music, and the singular brilliance of his voice.