In Solo Time — Richard J. Cass

An alcoholic walks into a bar . . . and buys it. At the urging of his sometimes lover and sometimes drinking partner Jacquie Robillard, Elder Darrow uses the last of the money from the trust fund his mother left him to buy the Esposito, a bucket-of-blood bar in Boston that he plans to turn into a jazz nightclub. But before he can turn the place around, the body of Timmy McGuire, a jazz guitar player, shows up on the small stage at the Esposito, stabbed to death.
Dan Burton, a Boston Homicide detective, likes Jacquie for the murder. She had a contentious relationship with the guitar player (and a few other men along the way). But one of the other men Jacquie is involved with is the son of an old-line Boston landlord with political designs on the commonwealth's governorship. Burton arrests Jacquie for Timmy McGuire's murder but Elder is certain something darker and deeper than a lover's quarrel is at stake.
Jacquie is released on bail. When she shows up dead, Elder is drawn into a conspiracy going back to Timmy's childhood, an arson in the three-decker in Mattapan where he grew up, and the unraveling of a political conspiracy. Elder's need to solve Timmy's murder peaks when his jazz singer lady friend, Alison Somers, is kidnapped by the perpetrators. In the end, he has to solve the mystery and rescue Alison without the help of the police or anyone else.