Hitchcock didn’t want music in Psycho’s shower scene. He practically doubled Herrmann’s salary after seeing the scene with music.

The shower scene in which Janet Leigh dies is one of the most famous horror scenes of all time. What most people don’t know is that the music used, a cacophony of “screeching violins, violas, and cellos,” almost didn’t make it into the movie.

Hitchcock wanted the scene to play completely without music until Bernard Herrmann insisted he view the scene with the music he had made for it. Hitchcock agreed that the music greatly added to the wow-factor of the scene. He liked it so much that he more or less double Herrmann’s salary! Another interesting fact about the shower scene has to do with the blood used in the scene.

Because the movie was filmed in black-and-white, the substance they used for the blood didn’t actually have to be red. For this reason, they didn’t use stage blood, which oftentimes is too thin to look like blood. Instead, they used chocolate syrup, which is much thicker. They also used the sound of a knife going into a melon for the sound of Leigh being stabbed.

(Source)