the crimes of the black cat (1972)

aka Seven Shawls of Yellow Silk. Sette scialli di seta gialla.
"Do you want me to detail our activities for the evening?"
Blind pianist Peter Oliver (Anthony Steffen) overhears part of a conversation whilst waiting for his girlfriend. He subsequently receives a note saying she was leaving him. So when she is found dead, he is the first to be questioned. Peter then replays the overheard conversation, believing it may give him a clue to the murderer.
A mix of a number of other film plot lines, done in an understated way, allow for a fine build up to the inevitable, but shocking, crescendo.