JLCooper MCS3 SP USB for OSX - Manual (Page 20)

All MIDI messages except for system exclusive are either one, two or three bytes long.
The first byte always is the message type, called the status byte. If there is a MIDI
channel, it is embedded in the status byte. The bytes following the status byte, if any,
are referred to as data bytes and contain additional information such as note numbers,
velocities, control values, etc...
If you choose a message type that is more than one byte long the 1st Data Byte ( and
possibly the 2nd Data Byte) editor appears. You can set the data byteʼs value by typing
or using the up/down arrows. The editor accepts values from 0 through 127.
Instead of setting an absolute value for a data byte, you can check the Follows
Controlʼs Value box. In this case, the value of that data byte is determined by the state
of the MCS3 SP hardware control this message is assigned to. In other words, if you
assigned a Custom MIDI Message to the Jog Wheel and the 2nd data byte was set to
Follows Controlʼs Value, a number representing the movement of the Jog Wheel
would be inserted as the 2nd data byte of the custom message. For MCS3 SP buttons,
a value of 127 will be inserted for button presses, and 0 for button releases.
Following are some samples of the MIDI Tabʼs appearance for various message types.
MCS3 SP USB Software
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