Csound can receive MIDI events (like MIDI notes and MIDI control changes) from an external MIDI interface or from another program via a virtual MIDI cable. This information can be used to control any aspect of synthesis or performance.
Most frontends are using their own MIDI handler. See the chapters about CsoundQt, Cabbage and Blue in this manual, or have a look at the built-in documentation of these environments. The following description is only relevant when you use Csound's own MIDI handlers, for instance when running Csound via Command Line.
Csound receives MIDI data through MIDI Realtime Modules. These are special Csound plugins which enable MIDI input using different methods according to a specific platform. They are enabled using the -+rtmidi command line flag in the <CsOptions> section of your .csd file.
There is the universal "portmidi" module. PortMidi is a cross-platform module for MIDI I/O and should be available on all platforms. To enable the "portmidi" module, use the flag (option):
-+rtmidi=portmidi
After selecting the RT MIDI module from a front-end or the command line, you need to select the MIDI devices for input and output. These are set using the flags -M and -Q respectively followed by the number of the interface. You can usually use:
-M999
To get a performance error with a listing of available interfaces.
For the PortMidi module (and others like ALSA), you can specify no number to use the default MIDI interface or the 'a' character to use all devices (which is actually the most common case). This will even work when no MIDI devices are present.
-Ma
So if you want MIDI input using the portmidi module, using device 2 for input and device 1 for output, your <CsOptions> section should contain:
-+rtmidi=portmidi -M2 -Q1
There is a special "virtual" RT MIDI module which enables MIDI input from a virtual keyboard. To enable it, you can use:
-+rtmidi=virtual -M0
If the "portmidi" module is not working properly for some reason, you can try other platform specific modules.
On Linux systems, you might also have an "alsa" module to use the alsa raw MIDI interface. This is different from the more common alsa sequencer interface and will typically require the snd-virmidi module to be loaded.
On OS X you may have a "coremidi" module available.
On Windows, you may have a "winmme" MIDI module.
Once you've set up the hardware, you are ready to receive MIDI information and interpret it in Csound. By default, when a MIDI note is received, it turns on the Csound instrument corresponding to its channel number, so if a note is received on channel 3, it will turn on instrument 3, if it is received on channel 10, it will turn on instrument 10 and so on.
If you want to change this routing of MIDI channels to instruments, you can use the massign opcode. For instance, this statement lets you route your MIDI channel 1 to instrument 10:
massign 1, 10
On the following example, a simple instrument, which plays a sine wave, is defined in instrument 1. There are no score note events, so no sound will be produced unless a MIDI note is received on channel 1.
EXAMPLE 02C01_Midi_Keybd_in.csd
<CsoundSynthesizer>
<CsOptions>
-+rtmidi=portmidi -Ma -odac
</CsOptions>
<CsInstruments>
;Example by Andrés Cabrera
sr = 44100
ksmps = 32
nchnls = 2
0dbfs = 1
massign 0, 1 ;assign all MIDI channels to instrument 1
instr 1
iCps cpsmidi ;get the frequency from the key pressed
iAmp ampmidi 0dbfs * 0.3 ;get the amplitude
aOut poscil iAmp, iCps ;generate a sine tone
outs aOut, aOut ;write it to the output
endin
</CsInstruments>
<CsScore>
</CsScore>
</CsoundSynthesizer>
Note that Csound has an unlimited polyphony in this way: each key pressed starts a new instance of instrument 1, and you can have any number of instrument instances at the same time.
To receive MIDI controller events, opcodes like ctrl7 can be used. In the following example instrument 1 is turned on for 60 seconds. It will receive controller #1 (modulation wheel) on channel 1 and convert MIDI range (0-127) to a range between 220 and 440. This value is used to set the frequency of a simple sine oscillator.
EXAMPLE 02C02_Midi_Ctl_in.csd
<CsoundSynthesizer>
<CsOptions>
-+rtmidi=virtual -M1 -odac
</CsOptions>
<CsInstruments>
;Example by Andrés Cabrera
sr = 44100
ksmps = 32
nchnls = 2
0dbfs = 1
instr 1
; --- receive controller number 1 on channel 1 and scale from 220 to 440
kFreq ctrl7 1, 1, 220, 440
; --- use this value as varying frequency for a sine wave
aOut poscil 0.2, kFreq
outs aOut, aOut
endin
</CsInstruments>
<CsScore>
i 1 0 60
</CsScore>
</CsoundSynthesizer>
Csound can receive other type of MIDI, like pitch bend, and aftertouch through the usage of specific opcodes. Generic MIDI Data can be received using the midiin opcode. The example below prints to the console the data received via MIDI.
EXAMPLE 02C03_Midi_all_in.csd
<CsoundSynthesizer>
<CsOptions>
-+rtmidi=portmidi -Ma -odac
</CsOptions>
<CsInstruments>
;Example by Andrés Cabrera
sr = 44100
ksmps = 32
nchnls = 2
0dbfs = 1
instr 1
kStatus, kChan, kData1, kData2 midiin
if kStatus != 0 then ;print if any new MIDI message has been received
printk 0, kStatus
printk 0, kChan
printk 0, kData1
printk 0, kData2
endif
endin
</CsInstruments>
<CsScore>
i1 0 3600
</CsScore>
</CsoundSynthesizer>
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