Four Flies on Grey Velvet (1971)
Italian-French co-produced giallo, directed and co-written by Dario Argento, and starring Michael Brandon and Mimsy Farmer. Roberto (Brandon) is the drummer in a rock band. One day he notices an odd-looking man in dark clothing, dark hat, and dark glasses following him. This continues for several days until one night after rehearsals he chases and corners the man, and during a brief struggle accidentally kills him. As Roberto realises what he has done he sees a masked figure photographing the whole scene. Over the following days, Roberto receives anonymous threatening letters, photographs of the killing, and the dead man's identity card. One night he is awoken by a noise. He goes in search of the cause and is attacked and strangled into unconsciousness. When he comes to he confides in his wife, Nina (Farmer), telling her everything. Soon after he consults a friend who suggests he hire a private investigator. He does so, but the threats keep coming - along with the murders of several people close to him.
Following its initial release, Four Flies on Grey Velvet became a very hard film to get hold of, even appearing on some lists as a 'lost film'. Argento has said that for 20 or so years Universal decided to withhold it for reasons that he never knew. Eventually, a change of leadership at the studio resulted in the film becoming more widely available. Like many 'lost films' it had acquired an almost mythical status, seen as a Holy Grail of sorts for Argento fans. Some of those fans hailed it as one of his best, whilst others found it something of a disappointment. It's beautifully shot (of course), and there are some great scenes - the early confrontation between Roberto and his mysterious stalker in an abandoned opera house, the pursuit and killing of one character trapped in a public park after closing, and the final fate of the guilty party. It also has a beautifully haunting score by Ennio Morricone. It falls down on some of the guilty party's actions, the fact that it becomes pretty easy to deduce who the killer is, and a motive which no amount of logic would allow anyone to deduce beforehand. It's worth a look for genre fans by virtue of its long unavailability, and I'm glad I've seen it; but I doubt I'll watch it again. 6/10
It's for free on Youtube, uploaded with its latest re-titling, Guns Knives Mace - Self-Defence for All. You won't learn anything of value, but it's very entertaining.
Thanks for the update! 
