Echo effects are commonly done with delays. Reverb effects simulate room characteristics, and are often adjustable to simulate different sizes and types of rooms. Reverb is often confused with echo, but rest assured, it's different. Flanging and Phasing. Two effects that are difficult to describe, but most everyone has heard both.
Pitch shifters increase or decrease the pitch of the sound.
This effect, combined with others, is what gives Darth Vader his characteristic voice. Effects processors can be used as inserts on channels or with aux sends. Also it allows mixing of the wet and dry signals, which is very desirable in most cases. Specifically, no warranty is expressed or implied regarding the accuracy of the information contained within. All trademarks are property of their respective owners.