Rack mounted effects processors are commonly used in recording studios and by sound re-enforcement hire companies at live shows and theatres. The point of creating the processors within a rack format is to save space and to have easy access to the effects unit when parameters are being changed. A rack formation allows the effects to be "stacked" on top of each other and utilise a very small footprint - this is the main advantage of rack configurations.
Effects racks will either be housed in wooden rack housings - sometimes with glass doors on the front - typically this is how they are presented in recording studios. Otherwise they are almost always housed in flight cases to be transported to and from venues. The standard rack width dimensions are 19" wide and 1 ¾" high although some rack effects may take up two or more rack "units".
Typical rack effects include compressors, limiters and noise gates along with the usual reverb, delay, pitch shifters and harmonisers. Many PA rental companies also have a rack for their power amps and a rack mounted CD is usually also included for playing incidental music through the house PA.
Professional musicians and particularly famous guitarists and bassists often have their own effects rack that contains all of the rack effects that provide them with their studio or on-stage sound.
