Requiem for a Mezzo by Carola Dunn (1996) 215 pages
This mystery is the third in a charming series featuring Daisy Dalrymple, set in Britain in 1923. Daisy's next door neighbor Muriel gives Daisy free tickets to a concert featuring Muriel's sister, Bettina, as the primary soloist. Muriel is in the chorus. Daisy invites Scotland Yard's Detective Chief Inspector Alec Fletcher to accompany her to the concert. As the intermission is ending and the second act is almost ready to begin, Bettina takes a drink and almost immediately dies on stage. Alec runs to take charge. As the chaos is sorted out, almost a dozen suspects bear scrutiny, including Muriel. It's clear that Bettina was not the easiest person to get along with. Several sexual dalliances are considered pertinent to the investigation, as are various strained family relations and issues between the singers in the cast.
In addition to solving the murder, Requiem advances the story line between Daisy and Alec. Jolly good fun.