Musical Instrument Digital Interface

MIDI Musical Instrument Digital Interface Enables electronic musical instruments, such as keyboard controllers, computers, and other electronic equipment, to communicate, control, and synchronize with each other.

MIDI Basics During the 1981 fall convention of the Audio Engineering Society, Dave Smith and Chet Wood, two engineers from synthesizer manufacturer Sequential Circuits proposed an industry standard for an electronic musical instrument interface. The goal was to create one type of connector that would allow synthesizers to connect to one another; regardless of manufacturer.

MIDI Basics MIDI came into use in 1983 MIDI isn’t hardware or software It’s a universal “digital language” and means of communication for music technology.

MIDI Basics

MIDI is completely independent of the audio circuitry— it’s not sound. L R AUDIO IN OUT THRU MIDI Note On; Note Number; Velocity; Note Off

MIDI MIDI doesn’t transmit digital audio. What it does transmit is the basic information supplied by the performer: What keys are pressed/released, and when What pedals are pressed etc.

MIDI devices communicate using messages … m e s s a g e s Note on Note off Program change Pitch bend Controller change Pressure (polyphonic) Pressure (monophonic)

MIDI Messages A MIDI interface allows the transmission and reception of 8-bit numbers. To play music, a language or protocol is needed to make sense of the numbers The numbers represent a great deal of data Note on Note off Program change Pitch bend Controller change Pressure (polyphonic) Pressure (monophonic)

Note On/Off When a key is pressed, a note-on message is transmitted When a key is released, a note-off message is transmitted C3 60 D3 62 E3 64 F3 65 G3 67 A4 69 B4 71 A#4 70 G#3 68 F#3 66 D#3 63 C#3 61 C2 48 D2 50 E2 52 F2 53 G2 55 A3 57 B3 59 A#3 58 G#2 56 F#2 54 D#2 51 C#2 49

Message Types Data System Message 111 MSByteLSByte Pitch Bend 110 (not used)Pressure Channel Aftertouch 101 (not used) Program Number Program Change 100 Value Controller Number Control Change 011 PressureNote Number Polyphonic Aftertouch 010 VelocityNote Number Note On 001 VelocityNote Number Note Off 000 Data Byte 2Data Byte 1Message TypeMessage bits

Control Change Other than the keyboard, several other controls affect the sound e.g. the volume knob, sustain pedal, modulation wheel etc. When any of these controls are adjusted, the new value is transmitted using a control change message. Controller number identifies the control to be altered (e.g. 1 = modulation, 7 = volume) The value can be either: A number between 0 and 127 for continuous controllers Either 0 or 127 indicating ‘off’ and ‘on’ for switches

Other Messages Aftertouch Polyphonic Aftertouch When a key is held down, pressure sensors can detect how hard it is pressed – this is known as aftertouch Channel Aftertouch Polyphonic aftertouch keyboards measure the pressure for every key. Cheaper keyboards measure the average pressure for the whole keyboard – channel aftertouch. Pitch Bend A special controller that subtly changes the pitch of all notes played on a channel System Messages Various system specific message relating to timing and used for reprogramming synthesisers

Program Change Most electronic instruments are capable of producing a variety of sounds Different sounds are stored in memory and are known as programs (or patches, voices etc.) To select a different sound, a program change message is transmitted Note, this is only a two-byte message

MIDI Connections MIDI Ports IN OUT THRU IN IN – Receives MIDI information OUT OUT – Transmits MIDI information THRU THRU – Passes along MIDI information To next MIDI IN USB is quickly replacing the traditional MIDI Ports.

MIDI Connections Most MIDI devices have three sockets: MIDI In: Receives MIDI information MIDI Out: Transmits MIDI information MIDI Thru: Repeats exactly the ‘MIDI In’ signal Using the ‘Thru’ socket, more than one instrument can be controlled by a single MIDI output: INOUTTHRUINOUTTHRUINOUTTHRU ABC

MIDI Connections MIDI Cable A cable with a 5-pin DIN connector on each end.

MIDI Allows one to Connect several Devices together MIDI “Master” instrument The instrument that sends information Master IN OUT THRU Slave IN OUT THRU MIDI “Slave” instrument The instrument that receives information

MIDI also allows Instruments to talk with Computers Connecting a MIDI Interface IN OUT

PRIOR to USB, a MIDI Interface was needed. MIDI Interface A device that is used to connect a computer to a MIDI system Provides the MIDI IN and OUT ports for connection to a MIDI device Translates MIDI data into a computer’s own machine language

Early Applications In the early days of MIDI, most instruments had limited polyphony and could only play one voice (patch/program) at a time Using more than one instrument and MIDI connections, performers could: Build up more complex sounds by mixing multiple voices Create keyboard splits and cross-fades Control synthesizers with different devices (e.g. MIDI pedals, guitars, clarinets, violins etc.)

Multi-Timbral Instruments INOUTTHRUINOUTTHRUINOUTTHRU MasterChannel 1Channel 2 INOUTTHRU Channel 3 Etc. (i) (ii) INOUTTHRU Master Synthesiser Channel 1 Synthesiser Channel 2 Synthesiser Channel 3 Etc. Single Multi- timbral synthesiser

General MIDI In the original MIDI specification, no assumptions were made about the instruments being used in terms of: Program number allocations Controllers Polyphony (how many notes can be played at once) Patch 001 on one Synthesizer might be a Piano, while another Manufacturer used 001 for a Harp.... this created problems.

General Midi General MIDI synthesizers (e.g. all sound cards) now have a universal setup; Fixed program names and controller numbers for all instruments.

25 General MIDI Patch Numbers PC# Family 1-8 Piano Reed 9-16 Chromatic Percussion Pipe Organ Synth Lead Guitar Synth Pad Bass Synth Effects Strings Ethnic Ensemble Percussive Brass Sound Effects

MIDI Basics MIDI Channels There are typically 16 different channels that can be used on a multi-timbral synth. Instruments that can receive and play back MIDI information on more than one channel at a time Essentially 16 different sounds can happen at once. Channel 10 reserved for drums

MIDI Basics Multi-timbral MIDI Instruments Drums Ch. 10 Bass Ch. 1 Piano Ch. 2 Guitar Ch. 3 Sax Ch. 4

Benefits of Using MIDI Small File Size Tempo and pitch are completely independent of each other Locate and cue sections or specific points using measures and beats Performance and notation of a song

MIDI Applications Sequencing Records and plays back MIDI data

MIDI Applications Sequencing Records and plays back MIDI data A digital “player piano”

MIDI Applications Sequencing Records and plays back MIDI data A digital “player piano” Works similar to a multitrack recorder

MIDI Applications Sequencing Records and plays back MIDI data A digital “player piano” Works similar to a multitrack recorder May also include digital audio recording

Audio & MIDI Compare and contrast Working together

MIDI FILES Songtitle.mid Midi files come in several formats SMF 0: In MIDI format 0, all the separate tracks of the arrangement are mixed into a single track (mixdown). If the song is then loaded to a sequencer or notation program, it is impossible to tell which track is assigned to which instrument. SMF 1: Unlike in format 0, all the instrument tracks are shown separately, enabling editing and assignment of the corresponding voice/melody in the notation program. SMF 2: Midi format 2 is a somewhat rarer member of the SMF (Standard Midi File) family and is basically an enhancement of format 1. It distributes the various patterns to separate tracks.

MIDI Sites! You can download MIDI files and use them for a variety of applications: Listening pleasure! Create and arrangement for your ensemble Get printed music versions of songs you like Manipulate the MIDI file to make great sounding mixes.

MIDI Files The problem with MIDI is that the files often sound a bit lame ! However New Technology has begun to address this problem...

Smart Music and MIDI Smart Music Software has upgraded the use of the general MIDI file sound and has begun to integrate the use of audio samples for patches. Humanistic elements of performance have also been added: fluctuations in time, inflection, dynamics, etc.

In Summary: MIDI is not audio... It is a collection of on and off messages It is a type of language that allows devices to communicate information.