Chorus
A Chorus is an effect that makes a single sound seem like several similar sounds playing together, such as a choir of voices or a section of violins.
Think of a small choir: even if everyone sings the same note, there are small and subtle variations in pitch and timing between each voice. It is this imperfection that creates a rich, full, and "wide" sound.
The chorus effect simulates this electronically:
It takes the original audio signal and duplicates it.
This copy is slightly delayed and its pitch is subtly modulated up and down by an LFO (Low Frequency Oscillator).
The modulated copy is then mixed back with the original sound.
The result is a "bright," "undulating" sound with a sense of movement and depth. It's a very popular effect on guitars, keyboards, basses, and vocals to add body and dimension to the timbre.