(1) Computer hardware, typically excluding the CPU and system memory, that can be controlled and can send and receive data. Examples of devices include displays, disc drives, buses, and keyboards. (2) In audio generally, a piece of equipment or a software entity that produces, transforms, transmits, receives, or stores audio data. In MIDI, a piece of equipment or a software entity that responds to MIDI control or provides MIDI data. In Audio Queue Services, a source or destination for audio, such as a microphone or a loudspeaker.