A MIDI controller is any hardware or software that generates and transmits Musical Instrument Digital Interface (MIDI) data to MIDI-enabled devices, typically to trigger sounds and control parameters of an electronic music performance. They most often use a musical keyboard to send data about the pitch of notes to play, although a MIDI controller may trigger lighting and other effects. A wind controller has a sensor that converts breath pressure to volume information and lip pressure to control pitch. Controllers for percussion and stringed instruments exist, as well as specialized and experimental devices. Some MIDI controllers are used in association with specific digital audio workstation software. The original MIDI specification has been extended to include a greater range of control features. Features MIDI controllers usually do not create or produce musical sounds by themselves. MIDI controllers typically have some type of interface that the performer presses, strikes, blows or touches. This action generates MIDI data (e.g. notes played and their intensity), which can then be transmitted to a MIDI-compatible sound module or synthesizer using a MIDI cable. The sound module or synthesizer in turn produces a sound that is amplified through a loudspeaker. The most commonly used MIDI controller is the electronic musical keyboard MIDI controller. When the keys are played, the MIDI controller sends MIDI data about the pitch of the note, how hard the note was played and its duration. Other common MIDI controllers are wind controllers, which a musician blows into and presses keys to transmit MIDI data, and electronic drums. The MIDI controller can be populated with any number of sliders, knobs, buttons, pedals and other sensors, and may or may not include a piano keyboard. Many Audio control surfaces are MIDI-based and so are essentially MIDI controllers. While the most common use of MIDI controllers is to trigger musical sounds and play musical instruments, MIDI controllers are also used to control other MIDI-compatible devices, such as stage lights, digital audio mixers and complex guitar effects units. Types (hardware and software) The following are classes of MIDI (Musical Instrument Digital Interface) controller: The human interface component of a traditional instrument redesigned as a MIDI control device. The most common type of device in this class is the keyboard controller. Such a device provides a musical keyboard and perhaps other actuators (pitch bend and modulation wheels, for example) but produces no sound on its own. It is