Apple Logic Pro X - Manual (Page 793)

Chapter 23 Work in the Environment 793
Fader functions: MIDI events
Each fader has an Input definition and an Output definition.
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Input definition: Determines the types of MIDI events that can remotely control the fader.
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Output definition: Determines the types of MIDI events the fader sends out.
A fader can, therefore, convert one type of MIDI event to another. Most MIDI events consist of
three bytes:
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The first byte indicates the type and channel of the MIDI event (a note on channel 3, for
example).
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The second byte indicates the first data value (the pitch of a note event, for example).
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The third byte indicates the second data value (the velocity of a note event, for example).
A few MIDI events—program change and aftertouch—only use two bytes. Faders and
transformers always provide for three bytes, with the second byte being discarded when these
special, 2-byte messages are received.
Fader parameters are provided for setting the message type, MIDI channel, and the first data
value. Note that the message type and MIDI channel are actually combined in the resulting MIDI
event. The second data value is determined by the fader setting, or if the fader is being remotely
MIDI-controlled, by the incoming MIDI event.
The following are used to define the Input and Output parameters:
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Output (or Input): Defines the event type.
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Channel (1 to 16): Defines the MIDI channel of the event.
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-1- (0 to 127): Defines the first data byte of the event. In some cases, such as pitch bend, this is
an actual data value. In other cases, such as MIDI controllers, this indicates the controller type
(volume, pan, and so on). In other cases, such as aftertouch, this byte is unused.
The -1- parameter options are described here, including how the fader position affects them (for
both the Input and Output definitions):
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Note On: The -1- parameter sets the pitch, and the fader position sets the velocity. This is most
useful as an Input definition, for trapping specific notes and converting them to other MIDI
events, or simply monitoring their velocity. If you move a fader with an Output definition set
to Note On, a note off MIDI event immediately follows the note on. This might be useful for
creating onscreen drum pads from button style faders, for example.
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P-Press: The -1- parameter sets the pitch, and the fader position sets the amount of Poly
Pressure (key pressure or polyphonic aftertouch).
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Control: The -1- parameter sets the MIDI controller number (the controller type), and the fader
position sets the controller value. The controller type can actually be selected by name, via the
pop-up menu that appears when you click-hold the -1- parameter.
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Program Change: The -1- parameter is ignored. The fader position determines the
program number.
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C-Press: The -1- parameter is ignored. The fader position sets the channel pressure
(monophonic aftertouch) amount.
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PitchBd: The -1- parameter sets the pitch bend LSB, and the fader position sets the MSB.
Typically, you would set the -1- parameter to 0, and use the fader to control the coarse pitch
bend amount. A -1- setting of 0, and a fader position of 64, results in no pitch bend.
SysEx and Switcher/Meta are special functions of the faders.