sliders and
media playback controls, which can manipulate the parameters of software or hardware instruments, effects, mixers and recording devices. MIDI was primarily designed with
musical keyboards in mind, and controllers that are not keyboards were once referred to as "alternate" controllers. The standard has nonetheless proved adaptable, and a wide variety of devices and instruments are now able to generate or respond to MIDI information. There is no clear definition of a MIDI controller: there are many purpose-built controllers designed to resemble instruments, but many
electronic instruments explicitly designed to be MIDI controllers (such as hardware
synthesizers) and other tools such as
music sequencers and
audio control surfaces can also produce MIDI output. Various devices use
MIDI Machine Control (MMC) messages to synchronize playback across hardware, and
MIDI Show Control (MSC) commands can even be used to coordinate sound, lighting and pyrotechnics in theatrical productions. In the narrow sense, most purpose-built musical MIDI controllers feature some prominent interface that the performer presses, touches, strikes or blows to send note information. They are often also equipped with a number of buttons, wheels, knobs, sliders, pedals, or other sensors for sending
control change events: these can be used to control parameters such as velocity and
pitch bend within other physical devices or
software synthesizers, providing another dimension of control for a performer. There also exist other types of controllers, such as pitch-to-MIDI converters, which analyze the pitch or vibrations of a traditional instrument or a voice and convert it to a MIDI signal in real time. Such devices have included the Roland CP-40 and the Fairlight Voicetracker, although these would usually now be replaced with
pitch-tracking software. Specific guitar-to-MIDI interfaces, often attached to a guitar using a special
pickup, have included the Shadow SH075, the IVL Pitchrider, and the Roland GI-10. MIDI controllers are conventionally connected to other devices using a MIDI cable, but an increasing number support
USB, which is more versatile and widely used. Software applications still recognize such controllers as MIDI devices, and a USB-equipped controller can normally draw all of the power it needs via a USB connection, removing the need for an
AC adapter.
Keyboards Keyboards are by far the most common type of MIDI controller and are available in various sizes, ordinarily from 25 to 88 keys. When a key is played, the MIDI controller sends MIDI data describing the pitch of the note and its duration—most MIDI keyboards also send data about the velocity with which a key is pressed. MIDI keyboards normally include
pitch wheels, modulation wheels, and sockets for
pedals (especially
sustain pedals), as well as controls that transpose the pitch values of notes played by the performer between octaves. Many keyboard controllers offer the ability to split the playing area into
zones, each of which can be assigned to a different MIDI channel and can be set to play any desired range of notes. This allows a single playing surface to control a number of different devices. MIDI capabilities can also be built into traditional
keyboard instruments such as
grand pianos
Pedal keyboards can operate the pedal tones of a MIDI organ, or can drive a
bass synthesizer. Many
keytars—keyboards worn with a shoulder strap and held like a guitar—produce MIDI output as well.
Drum and percussion controllers resemble actual drum kits. The unit's sound module is mounted to the left. , consist of velocity-sensitive drum pads arranged in a grid. Drum controllers are the second most common type of MIDI controller. Pads that can trigger a MIDI device can be homemade from a
piezoelectric sensor and a practice pad or other piece of foam rubber.
Wind controllers Wind controllers allow MIDI parts to be played with the same kind of expression and articulation that is available to players of wind and brass instruments. They allow breath and pitch glide control that provide a more versatile kind of phrasing, particularly when playing sampled or
physically modeled wind instrument parts. Examples of such controllers include
Akai's
Electronic Wind Instrument (EWI) and Electronic Valve Instrument (EVI). The EWI uses a system of keypads and rollers modeled after a traditional
woodwind instrument, while the EVI is based on an acoustic
brass instrument, and has three switches that emulate a
trumpet's valves. Simpler breath controllers are also available. Unlike wind controllers, they do not trigger notes and are intended for use in conjunction with a keyboard or synthesizer.
Stringed instrument controllers A guitar can be fitted with special
pickups that digitize the instrument's output and allow it to play a synthesizer's sounds. These assign a separate MIDI channel for each string, and may give the player the choice of triggering the same sound from all six strings or playing a different sound from each. and MIDI-equipped violas, cellos, contrabasses, and mandolins also exist. Other string controllers such as the Starr Labs Ztar use a combination of fretboard keys and strings to trigger notes without needing a MIDI pickup. |A MIDI controller designed for use with a
smartphone. The phone docks in the center.
Specialized and experimental controllers DJ digital controllers may be standalone units or may be integrated with a specific piece of software. These typically respond to MIDI clock sync and provide control over mixing, looping, effects, and sample playback. MIDI triggers attached to shoes or clothing are sometimes used by stage performers. The Kroonde Gamma wireless sensor can capture physical motion as MIDI signals. Sensors built into a dance floor at the
University of Texas at Austin convert dancers' movements into MIDI messages, and
David Rokeby's
Very Nervous System art installation created music from the movements of passers-through. Software applications exist which enable the use of
iOS devices as gesture controllers. Numerous experimental controllers exist which abandon traditional musical interfaces entirely. These include the gesture-controlled
Buchla Thunder, sonomes such as the C-Thru Music Axis, which rearrange the scale tones into an isometric layout, and Haken Audio's keyless, touch-sensitive
Continuum playing surface. Experimental MIDI controllers may be created from unusual objects, such as an ironing board with heat sensors installed, or a sofa equipped with pressure sensors.
GRIDI is a large scale physical MIDI sequencer with embedded LEDs developed by Yuvi Gerstein in 2015, which uses balls as inputs. The
Eigenharp controller is a combination of a breath controller, a configurable series of multi-dimensional control keys, and ribbon controllers designed to control its own virtual instrument software. ==Auxiliary controllers==