Final answer:
The consistent, low-pitch background noise in psychedelic songs is called a c. drone. It is one of the distinctive sound effects used to create the genre's characteristic atmospheric soundscapes.
Step-by-step explanation:
In psychedelic rock, the consistent, low-pitch background noise that was often used is known as a c. drone. The various effects and techniques, including reverb, tremolo, phasing, and drone, were instrumental in shaping the distinctive sound of psychedelic music.
In this context, a drone refers to a continuous note or chord that sounds throughout a musical piece and is common in forms of music worldwide, providing a sonic foundation and creating atmospheric soundscapes.