Everyone knows the scheennigh—scheennigh—scheennigh noise from Psycho. But how was it made? Is it an actual note? Is it a set of actual chords? Is it being played back through a filter? Was the conductor stabbing the violin players during the recording?
Bonus question: how would you spell the noise?
Rhythm
If you listen to Bernard Herrmann’s original score on the soundtrack, it’s largely indistinguishable from the music you hear in the shower sequence (though there is additional audio of the knife–phffft!–penetrating Marion’s body). So I’m inclined to believe that it was a series of chords specifically written, orchestrated, and conducted, and not just some violinists going at it haphazardly. Herrmann certainly had the composing chops, and Hitchcock was too meticulous an artist to have such a critical scene left to chance.
Going by this example: the first very high-pitched sound, the most distinctive one, is a combination of a plucked pitch (or perhaps more than one?) plus other violins playing short sudden slides upwards, in a very high part of their range. The inevitable indeterminacy of this creates the cluster-chord effect, even though I’m 99% sure they’re working from specific notated pitches, as all the subsequent lower entries do so.
If you want to get more in depth re: the Psycho soundtrack, check out Howard Goodall on Bernard Herrmann from his “20th Century Greats” tv series (highly recommended, BTW). Start at 2:05 in the clip for a good overview of how Herrmann wrote the Psycho score (and achieved the “skREE skREE skREE” effect) and why it’s so important in the history of film music.