midichannelaftertouch
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## midichannelaftertouch

midichannelaftertouch — Gets a MIDI channel's aftertouch value.

## Description

midichannelaftertouch is designed to simplify writing instruments that can be used interchangeably for either score or MIDI input, and to make it easier to adapt instruments originally written for score input to work with MIDI input.

In general, it should be possible to write instrument definitions that work identically with both scores and MIDI, including both MIDI files and real-time MIDI input, without using any conditional statements, and that take full advantage of MIDI voice messages.

Note that correlating Csound instruments with MIDI channel numbers is done using the massign opcode for real-time performance,. For file-driven performance, instrument numbers default to MIDI channel number + 1, but the defaults are overridden by any MIDI program change messages in the file.

## Syntax

    midichannelaftertouch xchannelaftertouch [, ilow] [, ihigh]

## Initialization

ilow (optional) -- optional low value after rescaling, defaults to 0.

ihigh (optional) -- optional high value after rescaling, defaults to 127.

## Performance

xchannelaftertouch -- returns the MIDI channel aftertouch during MIDI activation, remains unchanged otherwise.

If the instrument was activated by MIDI input, the opcode overwrites the value of xchannelaftertouch with the corresponding value from MIDI input. If the instrument was NOT activated by MIDI input, the value of xchannelaftertouch remains unchanged.

This enables score p-fields to receive MIDI input data during MIDI activation, and score values otherwise.

| Adapting a score-activated Csound instrument.
See the MIDI interop opcodes section for details on adapting score driven instruments for MIDI or vice-versa.

## Examples

Here is an example of the midichannelaftertouch opcode. It uses the file midichannelaftertouch.csd.

Example 451. Example of the midichannelaftertouch opcode.

See the sections Real-time Audio and Command Line Flags for more information on using command line flags.

    <CsoundSynthesizer>
    <CsOptions>
    ; Select audio/midi flags here according to platform
    -odac    -M1  ;;;realtime audio out and midi in
    ;-iadc    ;;;uncomment -iadc if realtime audio input is needed too
    ; For Non-realtime ouput leave only the line below:
    ; -o midichannelaftertouch.wav -W ;;; for file output any platform
    </CsOptions>
    <CsInstruments>

    sr = 44100
    ksmps = 32
    nchnls = 2
    0dbfs  = 1

    instr 1

    midinoteoncps p4, p5				;puts MIDI key translated to cycles per second into p4, and MIDI velocity into p5
    kafter init 127					;full open
    midichannelaftertouch  kafter
    printk2 kafter					;display the key value when it changes and when key is pressed

    kvel = p5/127					;scale midi velocity to 0-1
    kenv madsr 0.5, 0.8, 0.8, 0.5			;amplitude envelope multiplied by
    ain  pluck kenv*kvel, p4, p4, 2, 1		;velocity value
    asig moogvcf2 ain, 200+(kafter*40), .5		;scale value of aftertouch and control filter frequency
         outs  asig, asig				;base freq of filter = 200 Hz

    endin
    </CsInstruments>
    <CsScore>
    f 0 30	;runs 30 seconds
    f 2 0 4096 10 1

    i 1 0 2 440 100	; play these notes from score as well
    i 1 + 2 1440 100
    e

    </CsScore>
    </CsoundSynthesizer>

Its output should include lines like:

     i1   127.00000
     i1    20.00000
     i1    44.00000

## See Also

midicontrolchange, mididefault, midinoteoff, midinoteoncps, midinoteonkey, midinoteonoct, midinoteonpch, midipitchbend, midipolyaftertouch, midiprogramchange

## Credits

Author: Michael Gogins

New in version 4.20

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