Giallo napoletano aka Neapolitan Mystery 1979, Atrocious Tales of Love and Death, Giallo IT+(eng sub)

Mastroanni plays a mandolin player who, while trying to cover his senile fathers gambling debts, is sent to perform a serenade at a high rise building and witnesses a shootout and a man being thrown from a window to his death (the first of several falls from windows that the beleaguered hero witnesses). He gets mixed up with a famous conductor and his gorgeous wife as well as with the conductors beautiful daughterinlaw. The whole thing involves a confusingly intricate blackmail plot and a horrible secret dating back to World War II.