The Scottish poet and writer Jackie Kay is listening to Jazz Record Requests on the radio when I arrive at her home in Manchester, where she has lived for many years. She was startled recently to hear her own name on the show, when a listener asked for a song by Bessie Smith after reading Kay’s biography of the blues legend. “I grew up in a house filled with jazz,” she says, reaching for her mother’s best teacups – there are macaroons and biscuits on the table. Her parents loved to riff off each other in song: “What a day...