Musical Instrument Digital Interface

1982 very efficient method for representing music, for lighting, computer games and effects. low cost widespread

Midi data files are small compared to PCM files.PCM:10mb per minute MIDI:kb per minute MIDI only contains instructions needed by a synthesizer to play sounds 

MIDI messages - instruct synthesizer which sound to use, which notes to play and how loud to play each note. actual sounds from synthesizer easily compose and edit music 

MIDI stream uni-directional asynchronous bit stream at 31.25 kbits/sec. with 10 bits transmitted per byte (a start byte, 8 data buts, and one stop byte). three different MIDI connectors - IN- OUT- THRU 

MIDI data stream is usually originated by a MIDI controller, such ad a musical instrument keyboard, or by a MIDI sequencer. MIDI data output from a midi controller or sequencer is transmitted via the devices' MIDI OUT connector. The recipient of this MIDI data stream is commonly a MIDI sound generator or a sound module, which will receive MIDI IN connector, and respond these messages by playing sounds. The single physical MIDI channel is divided into 16 logical channels by the inclusion of a 4 bit Channel number within many of the MIDI messages. A musical instrument keyboard can general by set to transmit on any one of the 16 MIDI A MIDI sound source, or sound module can be set to receive on specific MIDI channel(s). 

Information received on the MIDI IN connector of a MIDI device is transmitted back out (repeated) at the devices' MIDI THRU connector. Several MIDI sound modules can be daisy-chained by connecting the THRU output of one device to the IN connector of the next device in the chain.  

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