The MIDI Protocol - Musical Instrument Digital Interface

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Information about The MIDI Protocol - Musical Instrument Digital Interface

Published on February 21, 2014

Author: BhaumikBhatt4



This presentation walks you through the basics of the MIDI protocol. An abbreviation for Musical Instrument Digital Interface, MIDI is an industry standard communications protocol used for electronic musical instruments and other stage, sound, control equipment, to talk to each other.

Audio Engineering

MIDI • MIDI (Musical Instrument Digital Interface); is an industry-standard protocol that enables electronic musical instruments and other equipment to communicate, control and synchronize with each other and to exchange system data • Devices such as computers, synthesizers, keyboard controllers, sound cards, samplers and drum machines • MIDI does not transmit an audio signal or media! • The sounds are generated by the synthesizer, which receives the MIDI data

History • By the end of the 1970s, devices from different manufacturers were generally incompatible with each other. At the control level, they had their own specific laws for defining voltage to pitch conversions • Dave Smith proposed a digital standard for musical instruments at the Audio Engineering Society show in New York • The MIDI Specification 1.0 was established in August 1983 • The MIDI specification has been re‐released many times since, listing new features • In 1990, the International MIDI Association changed its name to the MIDI Manufacturers Association, MMA


MIDI Ports • MIDI-In Port allows data to be received by a MIDI-compliant device • MIDI-Out Port is used for transmitting data • MIDI-Thru Port is used for linking a no. of MIDI devices with a single transmitter


New Interfacing methods

Networks A MIDI network is a combination of hardware and software that provides interconnectivity between a group of MIDI devices, such as synthesizers, controllers, and sequencers

Protocol • • • • • MIDI is a serial stream of data Runs at 31250 bits per second baud rate Describes event information Asynchronous transmission A 'standard' MIDI word consists of three bytes: The first is a Status byte, the second and third are Data bytes • All status bytes have their MSB set to 1, whereas all data bytes have it set to 0

Messages • MIDI messages commonly have at least one COMMANDSTATUS byte and may have zero or more DATA bytes • Types of Messages: 1. Channel Messages 2. System Exclusive Messages 3. System Common Messages 4. System Real-Time Messages

Message Name Byte 1 Byte 2 Byte 3 Example Channel Messages 1000 cccc The MIDI key The velocity specifies specifies the number 83 3D 79 turns note 3D (decimal 61) on channel 3 off how quickly the noteof the key or note to with a velocity of 79 (decimal 121). release is affected. release. Note On 1001 cccc The MIDI key specifies the number of the key or note to turn on. The velocity specifies how quickly or 94 3D 79 turns note 3D (decimal 61) on channel 4 on forcefully the note is with a velocity of 79 (decimal 121). struck. Polyphonic Aftertouch 1010 cccc The MIDI number. The key pressure value. Control Change 1011 cccc The controller number The controller [0 - 119] [0 - 127] Program Change 1100cccc The new program -- n/a -(patch) number. C3 44 changes the program number for MIDI channel 3 to 44 (decimal 68). 1101 cccc The single greatest pressure value of all -- n/a -depressed keys. D3 44 changes the channel-pressure for MIDI channel 3 to 44 (decimal 68). Note Off Channel Pressure (Aftertouch) Pitch Change Bend) Wheel (Pitch 1110 cccc key A0 3D 5A changes the pressure for note 3D (decimal 61) on channel 0 to a value of 5A (decimal 90). value B3 10 7F sets the value of controller number 10 (decimal 16) to 7F (decimal 127). Least significant 7Most significant 7-bits E1 70 37 sets the pitch-bend for channel 1 to a value bits of pitch-bend of pitch-bend value. of 03F8 (decimal 1016). value.

System Exclusive Messages • System Exclusive Messages are generally longer MIDI messages that are used for a variety of purposes • One of the primary purposes of the SysEx message is to send manufacturer-specific data to a MIDI synthesizer • Each SysEx message begins with two data bytes F0 (1111 0000) and 0iiiiiii, where iiiiiii is a manufacturer's code and equipment only responds to messages with the correct manufacturer's code • The SysEx message is terminated when the byte value F7 (1111 0111) is encountered

System Common Messages Message Name Byte 1 Byte 2 Byte 3 System Exclusive F0 (1111 0000) The manufacture's identifier. unique Reserved F1 (1111 0001) -- n/a -- -- n/a -- Song Position Pointer F2 (1111 0010) Least significant 7-bits. Most significant 7-bits. Song Select F3 (1111 0011) The song or sequence to be -- n/a -played. Reserved F4 (1111 0100) -- n/a -- -- n/a -- Reserved F5 (1111 0101) -- n/a -- -- n/a -- Tune Request F6 (1111 0110) -- n/a -- -- n/a -- System Exclusive END F7 (1111 0111) -- n/a -- -- n/a -- -- n/a --

System Real-Time Messages Message Name Byte 1 Byte 2 Byte 3 Timing Clock F8 (1111 1000) -- n/a -- -- n/a -- Reserved F9 (1111 1001) -- n/a -- -- n/a -- Start FA (1111 1010) -- n/a -- -- n/a -- Continue FB (1111 1011) -- n/a -- -- n/a -- Stop FC (1111 1100) -- n/a -- -- n/a -- Reserved FD (1111 1101) -- n/a -- -- n/a -- Active Sensing FE (1111 1110) -- n/a -- -- n/a -- Reset FF (1111 1111) -- n/a -- -- n/a --

MIDI Controllers

Example 1. Note-On message: 0x90, 0x3C, 0x7F 2. Aftertouch message(s): 0xD3, 0x46 3. Note-Off message: 0x80, 0x3C, 0x46

Composition & File formats • MIDI composition and arrangement typically takes place using either MIDI sequencing/editing software on computers or using specialized hardware music workstations • MIDI data files are much smaller than recorded audio waveforms • The SMF specification was developed and is being maintained by, the MIDI Manufacturers Association (MMA) • Karaoke files display lyrics synchronized with the music in "follow-the-bouncing-ball" fashion, turning any PC into a karaoke machine

Synthesizer • A synthesizer is an electronic musical instrument that uses one or more sound generators to create waveforms which are then processed and combined in order to generate musical sounds • MIDI synthesizers produce musical tones and percussion based on the input of MIDI software messages

Sequencer • A music sequencer is an application or a device designed to record and play back musical notation • A MIDI sequencer is the electronic version of the musician in the MIDI world • A MIDI sequencer: a) records MIDI software message sequences b) replays MIDI software sequences with the appropriate timing c) provides some sort of editing capabilities • The terms "Music Sequencer" and "Digital Audio Workstation" are often used interchangeably

Sampler A sampler is an electronic musical instrument which plays back recordings (or “samples") that are loaded or recorded onto it to perform or compose music

Software samplers

MIDI Standards Patch Family Name Patch Family Name 1-8 Piano 65 - 72 Reed 9 - 16 Chromatic Percussion 73 - 80 Pipe 17 - 24 Organ 81 - 88 Synth Lead 25 - 32 Guitar 89- 96 Synth Pad 33 - 40 Bass 97 - 104 Synth Effects 41 - 48 Strings 105 - 112 Ethnic 49- 56 Ensemble 113 - 120 Percussive 57 - 64 Brass 121 - 128 Sound Effects

Musical Applications • You can use a MIDI instrument with which you’re comfortable to play the sounds belonging to any other MIDI device. • Create rich musical textures by layering sounds from multiple MIDI devices, or assign different sounds to play in different pitch ranges. • When you play a MIDI instrument, it produces data that can be captured by a MIDI “sequencer.” Sequencers aren’t just MIDI recorders, they let you fix mistakes, change the pitches of your notes, fix their timing, the way they play, the sounds they use, and more.


LED 1 LED 2 LED 3 LED 4 LED 5 LED 6 LED 7 LED 8 LCD SW1 SW2 SW3 Sends 0x90, 0x24, 0x7F to PC ^ B TX SW4 RX UART 1 PC

LED 1 LED 2 LED 3 LED 4 LED 5 LED 6 LED 7 LED 8 LCD SW1 SW2 SW3 ^ Sends 0x91, 0x26, 0x7F to PC BS TX SW4 RX UART 1 PC

LED 1 LED 2 LED 3 LED 4 LED 5 LED 6 LED 7 LED 8 LCD SW1 SW2 SW3 Sends 0x92, 0x31, 0x7F to PC ^ BSC TX SW4 RX UART 1 PC

LED 1 LED 2 LED 3 LED 4 LED 5 LED 6 LED 7 LED 8 LCD SW1 SW2 SW3 Sends 0x93, 0x2E, 0x7F to PC ^ BSCH TX SW4 RX UART 1 PC

Non-musical Applications • • • • • • • • • • • Show control Machine control Theatre lighting Console automation Special effects Sound design Recording system synchronization Audio processor control Computer animation Computer networking Video Jockeys

We have come a long way...

References • 1. 2. 3. 4. 5. Webistes: Wikipedia ( How stuff works ( MIDI Manufacturers Association ( MIDI Reference from Tonalsoft ( • Books and eBooks: 1. eBook – MIDI and the AVR – ( 2. Audio Engineering: Know It All - Douglas Self 3. Audio Electronics, Second edition - John Linsley Hood

Thank You Bhaumik Bhatt

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