MIDI

Musical Instrument Digital Interface

MIDI

A data communications protocol that describes a means for music systems and related equipment to exchange information and control signals.

MIDI is not audio signal MIDI represents the information needed to

recreate a performance as many individual pieces of data.

MIDI Devices

Devices that can be controlled with MIDI include: Keyboards Synths Effects units MIDI Interface/Control Devices Lighting Boards Mixers Computer Programs – computers Fireworks

MIDI Equipment

MIDI Cable – 5 pin DIN connectors

MIDI Interface – Multiple inputs and outputs which can digitally route MIDI Messages on the fly, much like a patch bay.

MIDI Ports

MIDI IN Receives MIDI messages

MIDI OUT Transmits MIDI

MIDI THRU Makes a copy and passes through whatever

comes into the MIDI IN

MIDI Setups

This is a typical MIDI/Computer setup.

Additional devices can either be routed by the interface or connected to the MIDI THRU of the preceding device.

Devices can be directly routed to one another without the need of a computer or interface

MIDI Controllers

Keyboard Controllers They look like a keyboard but may just only transmit MIDI information.

No onboard sound creating engine. Wind Controllers, MIDI guitars, MIDI Drum sets. In a typical setup, the MIDI information will be transmitted to a sound

module which receives the messages and performs the notes. Synthesizer terminology

Monophonic/Polyphonic Keyboard Splitting – split points Mod wheel Pitchbend Hold/sustain Volume Velocity sensitive Aftertouch – Monophonic and Polyphonic

MIDI Controllers

Other Types of Controllers Numbered Controllers

Continuous Controllers• Mod Wheel

Bi-directional Controllers• Pitch Bend

Switch Controllers• On/off

But what do all these things do to make sounds?

MIDI Messages

MIDI uses binary code to transmit signals across the MIDI cable. This code informs the MIDI device receiving it how to act.

There are 16 channels that any device can either send or receive to over one MIDI cable. Some may send and receive on several at once. Main Types of MIDI Messages

Channel Messages• Channel Mode

• Channel Voice System Messages

• System Common Messages

• System Real-time

• System Exclusive

MIDI Messages

Channel Messages – specify a particular MIDI channel within the message and generally control aspects of performance. Channel Mode Messages are used primarily to select one of the

four MIDI modes for a device.

Mode 1 – Omni On/Poly Mode 2 – Omni On/Mono Mode 3 – Omni Off/Poly Mode 4 – Omni Off/Mono – multitimbral

• Multi Mode - in Mode 4 each channel acts polyphonically up to the polyphonic capability of the device.

MIDI Message Format

All MIDI information coded in bytes 7 data bits and 1 message type bit (MSB)

MSB = 1 means System Message MSB = 0 means Channel Message

7 data bits: range of values 0-127

Messages sent in “packets” 1st Byte: “Status Byte” has channel and type 2nd Byte: data one 3rd Byte: data two (some messages only)

MIDI Messages

Channel Voice Messages Note On Note Off Channel Pressure (aftertouch) Polyphonic Key Pressure (aftertouch) Program Change Control Change – affects parameters of notes that are

already “on”. See MIDI 1.0 Detailed Spec.• 127 different parameters.• Continuous Controllers• On/Off switch Controllers• Data Controllers• Undefined Controllers

MIDI Messeges

• Most Important Controller Numbers: 1 – mod wheel 2 – breath control 4 – foot controller 7 – main volume 10 – pan position 64 – sustain pedal 66 – sostenuto pedal 67 – soft pedal

PitchBend• Has much higher resolution, uses 14 bit resolution

References

Joseph Rothstein: MIDI: A Comprehensive Introduction

On Permanent Reserve in UT Fine Arts Library

MIDI Manufacturers Association (IMA) http://www.midi.org

General MIDI Patch Maps http://www.midi.org/about-midi/gm/gm1sound.s

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