Singer-songwriter Neil Sedaka, who marks his 50th anniversary in the music business this year, helped create what's known as the Brill Building sound in the late '50s and early '60s. He's been inducted into the Songwriter's Hall of Fame, but he got his start as a classical pianist. He joins Terry Gross to talk about his life as a performer — and about The Definitive Collection, a career-spanning greatest-hits compendium.