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 Messages sent in “packets”  1 st Byte: “Status Byte” has channel and type  2 nd Byte: data one  3 rd 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)  General MIDI Patch Maps  midi/gm/gm1sound.shtml#instrument midi/gm/gm1sound.shtml#instrument