Robert John "Bob" Gaudio (born November 17, 1942) is an American singer, songwriter, musician, and record producer, and the keyboardist and backing vocalist of the Four Seasons. Gaudio wrote or co-wrote and produced the vast majority of the band's music, including hits like "Sherry" and "December, 1963 (Oh, What a Night)". Though he no longer performs with the group, Gaudio and lead singer Frankie Valli remain co-owners of the Four Seasons brand.