After having a conversation with Herrmann, Hitchcock asked him not to make anything for the scene in the shower. Herrmann ignored and nowadays that is one of the most iconic movie scenes.
Possibly it is the darkest work of Hitchcock's career, a sort of macabre departure rooted in the tradition of American Gothic that came to show its bleak worldview. The black and buried humor that runs the film is morbid, fatalistic and pessimistic. Herrmann tried to reflect this obscure world and came up with an unprecedented solution in the history of film music - to restrict the orchestra to the string section, trying to "complement the black and white photograph of the film with music also in black and white." Herrmann rescued part of a composition from his youth, the "Sinfonietta for a String Orchestra," from which he drew motifs as the accompaniment to the scene in which Norman Bates talks about how horrible it would be to commit his mother to the mental asylum.
Ignoring the director's advice, he decided to compose music for the murder scene in the shower, one of his most risky musical ideas - the spectacular glissandi in one of the sharpest (almost unbearable to human ear) records of violins. The violins look like shouts, a musical paraphrase.
The score for Psycho is not only a masterpiece of the macabre that created school (possibly the shower scene, was the most imitated musical passage in the history of the cinema) but also an essential element to mark the tone of the film.
The credits theme, frantic, strident, based on the polyphony of several string sonorities, also describes a mental state of Norman Bates, disassociated between the fixation by the dead mother and her unstoppable compulsion to murder. The subject reappears in the scene where Marion leads the road, after stealing money, to Norman's motel, someone we do not yet know. Norman's shadow of his sick mind is not only insinuated, anticipating the musical plane rather than the sound, but the musical commentary also has much to do with the sense of guilt and sin that characterizes much of the cinema of Hitchcock. With its harrowing sound, the music describes Marion feeling guilty (having stolen the money) and is afraid of being discovered.
The rest of the score shows a gloomy, hopeless world, cruelly described by Hitchcock's camera. With great precision, the hitchcock camera slides into one of the windows of a building and shows us Marion and her lover, but their love relationship is marked by a melancholy tone, showing that it is impossible if they can not get money. This leads Marion to make the decision to steal the money on one of the most musically-acclaimed scenes in the film, while lacking dialogue, music and Hitchcock's careful planning are what show the character's dilemma between doing the right thing let yourself be carried away by temptation. A detailed plan of money that has been entrusted to Marion is shown on the bed of the same dormitory, at the same time that a repetitive ostinato that is associated with money is introduced. A traveling takes the money from the field of vision and takes us to Marion's suitcase (shows that she's going to get away with the money). While dressing and packing, the money remains out of the field of vision, but obsessive ostinato makes it present in your head at all times. Herrmann introduces disturbing violins on the ostinato - Marion's decision is taken and with it her fate is sealed. Many have argued that Herrmann was the greatest film composer ever to exist, but it is undeniable that due to his legacy in terms of musical structure, use of innovative instrumentation and compositional style, he remains one of the greatest influencers in the film scoring world.
-"Un Poco sobre bandas sonoras..y análisis de la música de algunas películas"
-"Cien Bandas Sonoras en la Historia del Cine" - Roberto Cueto https://www.linkedin.com/pulse/psycho-bernard-herrmann-bruno-bizarro/