A MIDI controller is an input device and electronic musical instrument which typically converts physical interaction to Musical Instrument Digital Interface (MIDI) information. This information can be sent to a sound module, synthesizer, or sampler, or can be recorded using a music sequencer or digital audio workstation for later playback. A MIDI controller may or may not have a synthesizer or speaker built in, and most rely on external equipment to convert MIDI events into an audio signal and then into audible sound.