Keyboard controller
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A keyboard controller is musical keyboard instrument that does not produce any sounds of its own. It is like a keyboard synthesizer minus the synthesis circuits, or sound module. It sends MIDI note data electronically to an external sound module, a synthesizer, or even a computer or music sequencer. In this way a keyboard controller can be used to take the place of several separate instruments.
A controller is used to "play a computer" as the sound data is not on the actual controller. The controller uses data on a computer to create sound, hence the term, "controller". With the controller one controls his or her computer, and plays music through it.
Controllers come in many variations, and send out data through a MIDI cable or USB. Through this the controller is connected directly to the computer, allowing the user to control the computer musically.
Controller features
Controllers vary in their "action" (the feel of the keys), the size and number of keys, additional included controls, computer interfaces and other features.
Keyboard controllers can be configured as mini keyboards with 28 miniature keys, mid-sized keyboards with 37, 44 or 66 keys, and full-sized keyboards with 88 piano keys.
Typical interfaces are MIDI DIN plugs and USB ports.
Almost all keyboard controllers include additional knobs, pads, buttons, wheels or other controls for pitch bend, sending MIDI control signals, rhythm input, instrument selection, transport control and other functions.