The Quartet Murders — J.R. Ellis

When Detective Chief Inspector Oldroyd witnesses the murder of a violin player at a concert at the Red Chapel Arts Centre in Halifax, the killer appears to vanish from the building. Motives seem to surround possession of the priceless instrument played by the victim. Oldroyd's investigations first take him into the ruthless world of rich instrument collectors but as he and DS Carter start to unravel the mystery, they uncover connections with dark events in the past. The Second Detective Chief Inspector Oldroyd Yorkshire Murder Mystery. Revised edition