The Listening Service explores the art of the cover version: what happens when one composer 'covers' the art of another? Why was it common practice for Baroque composers to recycle their own work and 'borrow' from their colleagues on a regular basis? And what of musical traditions like folk and jazz where key pieces or 'standards' are covered by multiple artists? Tom Service talks to Baroque expert Berta Joncas and folk star Eliza Carthy to get some answers.