The Killer Reserved Nine Seats (1974) Giuseppe Bennati

This is a surprisingly entertaining Italian giallo that resembles a lot of later American slasher movies more than it does the earlier or contemporary Italian thrillers. As in slasher films like "Stage Fright" (both versions), "Popcorn", and "Clown at Midnight" this film is basically about nine people who attend a showing at a mysteriously deserted theater and find themselves trapped inside and picked off one-by-one by a mysterious masked killer, who may be motivated by revenge. Really though the plot here is pretty inconsequential. 

This movie is much closer to the stylish gialli than amateurish slasher movies in quality, and instead of having a cast of adolescent American nitwits, the cast is made up of sumptuous European beauties who spend much of the movie in various states of undress--oh yeah, and the male lead from "South Pacific".