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					Musical Instrument Digital Interface

MIDI

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 Makes a copy and passes through whatever comes into the MIDI IN



MIDI THRU


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 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:


 
  

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1 – mod wheel 2 – breath control 4 – foot controller 7 – main volume 64 – sustain pedal 66 – sostenuto pedal 67 – soft pedal



PitchBend  Has much higher resolution, uses 14 bit resolution

USING MIDI
Common Messages, Industry Conventions, and General MIDI

MIDI SYNTHESIZERS
 MIDI

is “Real-Time” System  Describes music in “generic” terms  MIDI Synths “interpret” and “realize”  All MIDI Synthesizers are different
 

 All
 

MIDI Synthesizers fundamentally the same
All understand basic MIDI channel messages All allow user to select and play sounds by MIDI

Different programs, or “algorithms” Different types of sounds with different controls

MODEL: MASTER AND SLAVE
Keyboard (master) sends MIDI messages on a given channel  Synthesizer (slave) must be set to receive MIDI properly

 

Mode: Omni or Poly If Poly, then channel must be the same as the Master’s Note On/Note Off Continuous Control (MW, Pedals) Pitch Bend Program Change



Primary MIDI Messages:

 



NOTE ON/NOTE OFF MESSAGES
A
  

Note On msg is sent whenever a key is depressed on a MIDI keyboard
Contains current output MIDI channel Contains MIDI note number of key pressed Contains Velocity with which key was hit

A
 

Note Off msg is sent when a key is released
Should correspond to a preceding Note On msg Many companies use a 2nd Note On with velocity of zero, instead – Yamaha, for example

CONTINUOUS CONTROLLER MSGS
 Designed
  

to allow dynamic control of synthesizer parameters, for example:
Volume Control Vibrato Speed and Depth Timbre Changes (Filtering, modulation)

 CCs
 

are Channel Msgs with 2 data bytes

Data Byte 1: controller # (0-127) Data Byte 2: controller value (0-127)


Optionally, MSB/LSB with CC# + 32

PRIMARY RESERVED CC NUMBERS
 CC

0:  CC 1:  CC 4:  CC 6:  CC 7:  CC 10:  CC 64:  CC 123:

Bank Select Modulation Wheel Modulation Pedal Data Entry Volume Pan Position Sustain Pedal All Notes Off

MIDI PROGRAM CHANGE MSG
PC message used to change the sound on a particular MIDI channel  Channel Message with 1 Data Byte  Also called “Patch Change” message  “Patch” comes from Modular Synths


A particular way of connecting modules  CPU: a sound generation program  Sometimes called a “voice”


MIDI PROGRAM CHANGE MSG


Available PC numbers: 0 – 127
Most manufacturers use 1 – 128  Some synthesizers have only 32 programs  Some have hundreds, divided into “Banks”




Approaches to Using More Programs:
Bank Select (CC# 0 and 32)  Kurzweil: PC 0-99 normal, 100-127 bank  Bank Select or PC 100 must come first


RECORDING MIDI DATA


“MIDI Sequencer”
Device or software program designed to record, edit, and play back MIDI data  Many different types, made by many different manufacturers  Typically modeled on multi-channel tape recorders: multiple independent tracks  Every company saves sequencer data in a different, proprietary file format


INTRODUCTION TO CUBASE SX
Manufactured by Steinberg  DAW Software, like Nuendo  Unlimited MIDI and Audio Tracks  Recording, Editing, Mixing, Processing  Support for “Plugins” – Add-on Pgms  Supports most Audio, MIDI interfaces  Inter-application Communication via “Rewire”


STANDARD MIDI FILES
Extension to original MIDI 1.0 Spec  Provide a standard format for storing MIDI Sequencer Data  Three types of SMFs:


Format 0: 1 multi-channel track  Format 1: Multiple multi-channel tracks, track 1 is tempo map for all tracks  Format 2: Multiple tracks with independent tempos (not commonly used)


GENERAL MIDI


An industry standard set of sounds


Grouped by families (8 sounds in each)
Family PC# Family Piano 65-72 Reed Chromatic Percussion 73-80 Pipe Organ 81-88 Synth Lead Guitar 89-96 Synth Pad Bass 97-104 Synth Effects Strings 105-112 Ethnic Ensemble 113-120 Percussive Brass 121-128 Sound Effects

PC# 1-8 9-16 17-24 25-32 33-40 41-48 49-56 57-64

GENERAL MIDI


Channels 1-9, 11-16 standard use
Typically one sound per channel  Polyphonic (multiple voices, same sound)  Notes may sustain indefinitely




Channel 10 is “Drum Channel”
Each note number a different drum  Most notes simply trigger  Duration may be determined by velocity


GM DRUM KITS


Standard Kit (partial list):
Key# Drum Sound 59 Ride Cymbal 2 60 Hi Bongo 61 Low Bongo 62 Mute Hi Conga 63 Open Hi Conga 64 Low Conga 65 High Timbale 66 Low Timbale

Key# Drum Sound 35 Acoustic Bass Drum 36 Bass Drum 1 37 Side Stick 38 Acoustic Snare 39 Hand Clap 40 Electric Snare 41 Low Floor Tom 42 Closed Hi Hat


				
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posted:11/15/2009
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