My guest this week has a theory that everyone’s head is carrying a tune – a permanent soundtrack, a default earworm. Her own cerebrum is tuned to Jimi Hendrix’s All Along The Watchtower, which has special significance when she starts writing as she sees the process of plotting as the search for an escape. And her book centres on two characters who need this escape – sisters who were professional singers, who go through multiple misunderstandings before they find their equilibrium. (Cue Nina Simone: Don’t Let Me Be Misunderstood.) The author is Nadine Matheson and she’ll be here on Wednesday with her Undercover Soundtrack.