At least 20 unpublished stories by Anthony Burgess, the author of A Clockwork Orange, have been discovered by researchers. Photograph: Christopher Thomond for the Guardian

At least 20 unpublished stories by Anthony Burgess, the author of A Clockwork Orange, have been discovered by researchers sorting through his papers at a research centre in Manchester, the city in which he was born.

The short stories, unproduced film and theatre scripts and hundreds of musical compositions have emerged from the contents of three houses in London, Monaco and Italy, bequeathed to the International Anthony Burgess Foundation after the death of his widow, Liana, four years ago. Burgess died in 1993.

Among the archive are 50,000 books and 20,000 photographs, symphonies, poems and unfinished or rejected scripts for television and film projects, including lives of Atilla the Hun, Sigmund Freud and Michelangelo and a play about Harry Houdini that he collaborated on with Orson Welles, another frustrated creator of unproduced projects.