For the purposes of MCI, devices are classified as either:
Simple devices
Simple devices do not require a data file for playback. Videodisc players and compact disc (CD) audio players are examples of simple devices.
Compound devices
Compound Devices require a data file for playback. MIDI sequencers and waveform audio players are examples of compound devices. The data file associated with a compound device is known as a device element. Examples of device elements are MIDI files and waveform files.