Irving Berlin, 95 years old, started early. At the age of 14 in 1902, he was singing in saloons. Ten years later, he'd made 100,000 dollars in royalties and "Alexander's Ragtime Band" had sold two million copies. The songs poured out over the next 50 years, 3,000 of them, but he never learnt to read music and composed on a piano with an automatic key changing device. Sheridan Morley explores the phenomenon of Irving Berlin with Alan Jay Lerner, Andrew Lloyd Webber, Ethel Merman, Jerome Robbins, Steve Ross and Brian Rust.