Midi message formats

1. MIDI Messages: general concepts
The MIDI protocol is made up of a series of messages of 8-bit
bytes.
The first byte of the message is the status byte, residing in the
range 128-255.
The remaining bytes of the message (called data bytes) will be in
the range 0-127.
The first bit of a status byte is always a 1; the first bit of a data
byte is always a 0.
There is 1 start bit, 8 data bits, and 1 stop bit, for a period of
320 microseconds per serial byte or 3,125 bytes per second.
MIDI transmits a variety of messages used to express different
musical attributes and performance functions.
(…….this is important!)

2. Note On
Q. Who’s on first?
A. Status byte = kind of event or function…..Data byte(s) follow(s) with the details.
01000000
00111100
10010000
MIDI OUT
MIDI IN
STATUS BYTE FOR
NOTE ON MESSAGE
DATA BYTE INDICATING
KEY #60 = MIDDLE C
DATA BYTE INDICATING
KEY VELOCITY = 64

3. Note off
01000000
00111100
10010000
MIDI OUT
MIDI IN
STATUS BYTE FOR
NOTE ON MESSAGE
DATA BYTE KEY #60
= MIDDLE C
DATA BYTE INDICATING
KEY VELOCITY = 64
00000000
00111100
DATA BYTE INDICATING
KEY VELOCITY = 0

4. Transmitting a C+ chord in root position
Note On/Note Off/Velocity
01000000
00111100
10010000
MIDI OUT
MIDI IN
STATUS BYTE FOR
NOTE ON MESSAGE
DATA BYTE KEY #60
= MIDDLE C
DATA BYTE
KEY VELOCITY = 64
01000000
01000100
01000011
00111111
00111100
00000000
0100000000000000
0100001100000000
DATA BYTE KEY #64
= E above mid. C
DATA BYTE KEY #64
= G above mid. C
DATA BYTE E KEY
VELOCITY = 68
DATA BYTE G KEY
VELOCITY = 63

5. Controllers
MIDI allows for up to 121 devices that transmit
Control Change Messages between values of 0 – 127.
Standard MIDI Controller #s. 0 - 63 designate
continuous message devices i.e. 1 = mod. wheel, 4 =
foot pedal, 7 = volume pedal.
Controllers 64 - 120 designate switch devices with
values 64 - 127 = On.
Pitch change messages provide 16,384 steps of
resolution to accommodate the ear’s acute sensitivity
to pitch.
Excessive use of controllers in a dense musical
arrangement can lead to an overload of MIDI’s
transmission capacity.

6. Example of Continuous Data Controller
01000000
00111100
10010000
MIDI OUT
MIDI IN
STATUS BYTE FOR
NOTE ON MESSAGE
10110000
00000010
01000011
00000110
00000111
00001010
0000011100010001
0100001100000000
DATA BYTE KEY #64
= G above mid. C
DATA BYTE BREATH
CTLR. = 2
STATUS BYTE FOR
CTL. CHANGE MESSAGE

7. Pitch Bend
01000000
00111100
10010000
MIDI OUT
MIDI IN
STATUS BYTE FOR
NOTE ON MESSAGE
11100000
00000000
00000110
MOST SIGNIFICANT
DATA BYTE
LEAST SIGNIFICANT
DATA BYTE
STATUS BYTE FOR
PITCH CHANGE MESSAGE
ETC……...

8. Program Changes
00111100
11000000
MIDI OUT
MIDI IN
STATUS BYTE FOR
PGM. CHANGE
MESSAGE
DATA BYTE INDICATING
PRESET PROGRAM
NUMBER

9. Channels and Modes
MIDI allows for up to 16 channels/cable port utilizing 4
possible modes to create elaborate multi instrumental
arrangements.
2nd nibble of a status byte is used to represent numbers 1 – 16.
Four possible combinations of Omni On/Off and Poly/Mono
are used to configure synths to respond or ignore channel
messages, or to operate in a poly- or monophonic mode.
Omni-On/Poly, Omni-On/Mono, Omni-Off/Poly, Omni-
Off/Mono.
Synthesizers have a limited number of available voices.

10. Practical Assignments:
Set up the following examples of Daisy Chains.
Test MIDI program change messages and channel assignments.
Test MIDI data flow from one device to the next.

IN THRU OUT
Keyboard*
Computer/
Sequencer
IN THRU OUT
* Omni-On (Off)/Poly Mode

11. Example of Daisy Chain

IN THRU OUT
IN THRU OUT
IN THRU OUT
Keyboard
Keyboard
Module

12. Example of Daisy Chain

IN THRU OUT
IN THRU OUT
IN THRU OUT
Keyboard
Keyboard
Module

13. Example of Daisy Chain

IN THRU OUT
IN THRU OUT
IN THRU OUT
Keyboard*
Keyboard
Module
Computer
IN THRU OUT
*CTL.TYPE SET TO BOTH/THRU???