M I D I Musical Instrument Digital Interface The MIDI protocol — a “language” that lets synthesizers, computers and other devices talk to each other.

The MIDI Language Messages use MIDI cables. Audio uses audio cables.

Note on MIDI Messages Note off Program change (patch change) Pitch bend Controller change Polyphonic pressure (aftertouch) Monophonic pressure (aftertouch)

MIDI Channels Ch 1: piano Ch 3: bass Ch 2: guitar Ch 4: tuba MIDI cable carries 16 channels

MIDI devices communicate using messages… Note on Note off Program change Pitch bend Controller change Pressure (polyphonic) Pressure (monophonic)

Audio MIDI USB A B IN OUT IN

Multi-port MIDI Interface (2 in/out pairs) IN A B OUT A B USB port Thru switch – connects In to Out, for use without a computer Leave in ‘out’ position! Lights!

Multi-port MIDI Interface (8 in/out pairs) Front Back MIDI OutputsMIDI Inputs USB port Each MIDI cable can carry 16 channels.

Two Kinds of MIDI Network MIDI Daisy-chain Network Purpose: provide pathways for MIDI messages Devices connected in series: MIDI Star Network Devices connected in parallel: interface

MIDI Daisy-chain Network IN OUT THRU IN THRU IN The 3 devices must share 16 channels. THRU port: transmits copy of messages from IN port

port 4 MIDI Star Network Each device has 16 channels all to itself. Any device can act as a controller. port 7 port 5 port 1

Pros and Cons MIDI Star Network MIDI Daisy-chain Network more accurate timing does not require multi-port MIDI interface more channels more than one device can act as controller

Local Control sound generator keyboard SynthesizerComputer echo and re-channelize local connection MIDI messages transmitted: Internally Over MIDI cables

MIDI Patch-thru and Re-channelizing Local control turned off. Synth transmits on channel 1. Sequencer echoes note back to synth on channel 2. Synth plays “Detox Lead.” MIDI USB Triton Le Sequencer: echo and re-channelize

MIDI Data Transmission Time Voltage What goes through the MIDI cable? lohilohilohilohilohilohilovoltage: Timed pulses of electricity – per second bits:

MIDI Data Encoding The bits encode numbers, in groups of 8 bits bits: byte stop bitstart bit = 163 decimal Byte: an 8-bit binary number

MIDI Message Bytes Each message contains one or more bytes… byte 1: Status Byte bytes 1-?: Data Bytes what type of message [e.g., note-on] what channel (for some message types) Stream of bytes parsed into MIDI messages. meaning depends on type of message each byte has a range from 0 to 127 [128 values]

MIDI Data Rate bits / second = bit bytes / second Typical messages have 2 to 3 bytes. So MIDI can handle between 1000 and 1500 messages per second. Sounds like a lot, but it’s easy to clog the stream with controller and pitch bend messages

Types of MIDI Message ChannelSystem MIDI Message ModeVoiceReal-timeCommonSysEx

Channel Voice Messages Data 2Data 1Type ValueNote numPoly pressure -ValueMono pressure ValueController numControl change Bend amountPitch bend -Program numProgram change VelocityNote numNote off Note numVelocityNote on All values 0 to 127, except Pitch bend: to 8191

Channel Voice Oddities Program change can select only 128 programs. Bank Select (a type of Control change message) lets you select 128 programs within each bank. Pitch bend has much wider range (16384 values). Why? Our ears more sensitive to pitch changes. Note off rarely used. Instead, note on with velocity = 0

Channel Voice Messages Data 2Data 1Type ValueNote numPoly pressure -ValueMono pressure ValueController numControl change Bend amountPitch bend -Program numProgram change VelocityNote numNote off Note numVelocityNote on All values 0 to 127, except Pitch bend: to 8191

Control Change Message One of the 7 Channel Voice messages Data byte 1: controller number Data byte 2: value [0-127] Lots of controller numbers in common use Effect on sound dependent on synthesizer patch

Common Control Change Messages 64Sustain (damper) pedal 7Volume 10Pan 6Data entry 4Foot controller 2Breath controller (JS-Y) Controller NumberController Name 1Modulation wheel (JS+Y) JS = Joy Stick; JS+Y = move joystick up along Y axis. Sustain pedal is a switch controller – it’s either on or off.

Timing in a MIDI Sequencer Measure | Beat | Tick Example:2 | 3 | nd measure 3 rd beat 120 th tick Tick: tiny, tempo-dependent unit of time 480 ticks per quarter note (by default in Digital Performer)

Ticks and Note Values quarter =480ticks 8 th =ticks 16 th =ticks 32 nd =ticks triplet 8 th =ticks

Quantization Notes (piano-roll) Show 8 th -note grid Quantize to 8 ths Snap notes to a rhythmic grid

1.An instrument that controls others [guitar controller, wind controller, keyboard controller, etc.] 2.Physical controls on an instrument [mod. wheel, data slider, foot pedal, breath controller, etc.] 3.MIDI control change messages [volume controller, pan controller, controller #6, etc.] Different meanings for “control,” “controller”

Synthesizer Polyphony ‘Polyphony’ means many voices. A synthesizer needs at least one voice to play one note. Korg Triton Le has 62 voices When you run out of voices, some notes will be cut short. Some sounds need more than one voice per note.

Synthesizer Polyphony Let’s say a synth has 8-note polyphony. Play a chord with 8 notes...Now play a new note while holding the others… One of the first notes stops sounding, even though you’re still playing it.