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when you pulled back on the pedal? Another question, how did your effects unit shut off the Delay effect when you
pressed a certain button on the MIDI controller? How did it know to turn it back on when you pressed the button again?
You guessed it, the CC message is responsible for all of those things.
A MIDI Channel can have up to 128 CC messages that it can respond to. They are numbered from 0 to 127. Since we
usually assign a single MIDI Channel to one device, it means that any one MIDI device in our system can respond its
own CC message from 0 to 127. Not all devices implement all 128 CC messages. Look at the devices MIDI
implementation guide to determine which CC messages it will respond to.
So how did the expression pedal change the volume? Let’s answer that while explaining the CC MIDI message. CC
messages have 3 parts to the command. First, we need to tell the command which MIDI channel (device) we are talking
to. Next, we need to tell the command which of the 128 CC numbers we are using. Finally, we need to tell the command
what data value we are storing in the CC#. CC data values are between 0 and 127.
There are a couple of conventions used for the data value worth noting. For commands that use CC numbers to turn
things ON and OFF, the data value of 0 usually represents OFF, and 127 represents ON. For effects like volume, the
entire range of values (from 0-127) are used to provide relative % of total value. So 0 is NO VOLUME and 127 would be
full VOLUME.
So putting it together, let’s assume a device on channel 1 has assigned CC#7 to Volume. Now we need to tell the
speaking device (like the Liquid Foot+ MIDI Controller with the expression pedal connected), that we will transmit the
expression pedal values to CC #7 on MIDI Channel 1.
When you press the expression pedal, the MIDI CONTROLLER will automatically figure out the position of the pedal
(with a value between 0 and 127), and automatically (continuously as you move the pedal) send the commands to the
device which will change the volume as you move the pedal.
The same concept is true for turning effects on and off. Let’s say an effects unit assigned CC#12 to Delay. We could send
a CC command to CC#12 as the CC number, with a value of 127 (ON). This will tell the effects unit to turn ON the delay.
If we sent a CC command to CC#12 with a data value of 0 (OFF), then the effects unit will shut of the delay effect.
On the LF+, this Command might look something like this on 2
nd
line of the LCD: 01 | 01|4| 012 | 127. The first 01 is
telling us that we are programming the first command of the sequence (perhaps the only command). The Second 01 is
the midi channel (the screen’s top line say “Midi Chan”. The 4 refers to the 4
th
midi command, and the top of the screen
says “CC #” so you know it's a Continuous Controller. The 12 is the CC# (our delay per above), and the 127 is the Data
Value (ON). So we have a CC#12 Message on MIDI Channel #1 with a Data Value of 127 (ON). Not too bad!