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.