order to accomplish the image of both twins conjoined onscreen in the film's finale (both played by Kidder), De Palma had Kidder photographed seated in two different positions, and then joined the images together via optical editing. Musical score While editing the film in post-production, editor Paul Hirsch and De Palma listened to musical scores by Bernard Herrmann (particularly for Psycho, Marnie, and Vertigo) and played them along with the film's key scenes. This led to De Palma inquiring about Herrmann composing the film's musical score. At the time Herrmann was semi-retired, but admired the screenplay enough to agree to score the film. Release Sisters had its world premiere at Filmex in Los Angeles, California on November 18, 1972. It was released theatrically in the United States by American International Pictures, opening in Los Angeles on April 18, 1973. It would later expand, opening in New York City on September 26, 1973, where it received "rave reviews," and continued to screen into November 9, 1973. It was also selected for the 1975 Venice Film Festival. Critical response Contemporaneous The film was met with critical praise; Roger Ebert noted that the film was "made more or less consciously as an homage to Alfred Hitchcock", but said it "has a life of its own" and praised the performances of both Kidder and Salt. Vincent Canby of The New York Times called it " a good, substantial horror film" and stated "De Palma reveals himself here to be a first-rate director of more or less conventional material", also noting the film's references to Repulsion (1965) and Psycho (1960). Meanwhile, Variety, while stating it was "a good psychological murder melo-drama", said that "Brian De Palma's direction emphasizes exploitation values which do not fully mask script weakness." The Los Angeles Timess Kevin Thomas praised it as a "witty homage to Hitchcock" and a "low budget but high style scare show," as well as praising the performances and musical score. George McKinnon of The Boston Globe was less laudatory, writing: "It is difficult to determine what De Palma had in mind in this morbid horror film. Did he intend it all as a parody or a straightforward Psycho-type movie? ... If it is to be taken as a tongue-in-cheek romp, it doesn't work and if meant as a horror film it is run-of-the-mill." The film received honors from the U.S. Film Festival in Dallas, Texas on