All the tunes

What links pre-War picker George Formby and Wagner, US rock duo The White Stripes and Bruckner, crooning legend Barry Manilow and Chopin? The surprising answer is that they've all shared tunes. Is that because, after 1,000 years of written music, there are no tunes left? What are the essential ingredients of a great tune and how difficult is it to write one? Tom Service seeks answers with the help of maths man Marcus du Sautoy and composer Jessica Curry. David Papp (producer)