Dead Beat by Val McDermid

Manchester private investigator Kate Brannigan specializes in white-collar corporate fraud, but she agrees to do a personal favor for her rock-journalist boyfriend: track down Moira Pollock, a missing songwriter who vanished from the music scene. Kate’s search leads her into the gritty underbelly of West Yorkshire, where she discovers Moira has left her past behind to build a quiet new life with her female partner, Maggie. But Moira’s reluctance to return becomes the least of Kate's problems when the songwriter is brutally murdered shortly after her location is compromised, leaving Kate to untangle a web of rock-and-roll ego, blackmail, and dangerous secrets to catch a killer.