Since control surfaces are designed to perform different functions, they vary widely in size, shape and number and type of controls. A basic control surface intended primarily for mixing resembles a traditional analogue mixer, featuring faders, knobs (rotary encoders), and buttons that can be assigned to parameters in the software. Other control surfaces are designed give a musician control over the sequencer while recording, and thus provide transport controls (remote control of record, playback and song position). Control surfaces are often incorporated into MIDI controllers to give the musician more control over an instrument.
Some control surfaces are designed to be used specifically with one piece of software, such as Digidesign's Digi 003 is for use with ProTools LE. Others are general purpose and can be used with many different software applications.
The control surface connects to the host computer via many different interfaces. MIDI was the first major interface created for this purpose, although many devices now use USB, FireWire, Ethernet or proprietary interfaces.