READING MIDI FILES
Instead of using either the standard Csound score or live midi events as input for a orchestra Csound can read a midi file and use the data contained within it as if it were a live midi input.
The command line flag to instigate reading from a midi file is '-F' followed by the name of the file or the complete path to the file if it is not in the same directory as the .csd file. Midi channels will be mapped to instrument according to the rules and options discussed in Triggering Instrument Instances and all controllers can be interpretted as desired using the techniques discussed in Working with Controllers. One thing we need to be concerned with is that without any events in our standard Csound score our performance will terminate immedately. To circumvent this problem we need some sort of dummy event in our score to fool Csound into keeping going until our midi file has completed. Something like the following, placed in the score, is often used.
f 0 3600
This dummy 'f' event will force Csound to wait for 3600 second (1 hour) before terminating performance. It doesn't really matter what number of seconds we put in here, as long as it is more than the number of seconds duration of the midi file. Alternatively a conventional 'i' score event can also keep performance going; sometimes we will have, for example, a reverb effect running throughout the performance which can also prevent Csound from terminating. Performance can be interrupted at any time by typing ctrl+c in the terminal window.
The following example plays back a midi file using Csound's 'fluidsynth' family of opcodes to facilitate playing soundfonts (sample libraries). For more information on these opcodes please consult the Csound Reference Manual. In order to run the example you will need to download a midi file and two (ideally contrasting) soundfonts. Adjust the references to these files in the example accordingly. Free midi files and soundfonts are readily available on the internet. I am suggesting that you use contrasting soundfonts, such as a marimba and a trumpet, so that you can easily hear the parsing of midi channels in the midi file to different Csound instruments. In the example channels 1,3,5,7,9,11,13 and 15 play back using soundfont 1 and channels 2,4,6,8,10,12,14 and 16 play back using soundfont 2. When using fluidsynth in Csound we normally use an 'always on' instrument to gather all the audio from the various soundfonts (in this example instrument 99) which also conveniently keeps performance going while our midi file plays back.
EXAMPLE 07D01_ReadMidiFile.csd
<CsoundSynthesizer>
<CsOptions>
;'-F' flag reads in a midi file
-F AnyMIDIfile.mid
</CsOptions>
<CsInstruments>
;Example by Iain McCurdy
sr = 44100
ksmps = 32
nchnls = 1
0dbfs = 1
sr = 44100
ksmps = 32
nchnls = 2
giEngine fluidEngine; start fluidsynth engine
; load a soundfont
iSfNum1 fluidLoad "ASoundfont.sf2", giEngine, 1
; load a different soundfont
iSfNum2 fluidLoad "ADifferentSoundfont.sf2", giEngine, 1
; direct each midi channels to a particular soundfonts
fluidProgramSelect giEngine, 1, iSfNum1, 0, 0
fluidProgramSelect giEngine, 3, iSfNum1, 0, 0
fluidProgramSelect giEngine, 5, iSfNum1, 0, 0
fluidProgramSelect giEngine, 7, iSfNum1, 0, 0
fluidProgramSelect giEngine, 9, iSfNum1, 0, 0
fluidProgramSelect giEngine, 11, iSfNum1, 0, 0
fluidProgramSelect giEngine, 13, iSfNum1, 0, 0
fluidProgramSelect giEngine, 15, iSfNum1, 0, 0
fluidProgramSelect giEngine, 2, iSfNum2, 0, 0
fluidProgramSelect giEngine, 4, iSfNum2, 0, 0
fluidProgramSelect giEngine, 6, iSfNum2, 0, 0
fluidProgramSelect giEngine, 8, iSfNum2, 0, 0
fluidProgramSelect giEngine, 10, iSfNum2, 0, 0
fluidProgramSelect giEngine, 12, iSfNum2, 0, 0
fluidProgramSelect giEngine, 14, iSfNum2, 0, 0
fluidProgramSelect giEngine, 16, iSfNum2, 0, 0
instr 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16 ; fluid synths for channels 1-16
iKey notnum ; read in midi note number
iVel ampmidi 127 ; read in key velocity
; create a note played by the soundfont for this instrument
fluidNote giEngine, p1, iKey, iVel
endin
instr 99 ; gathering of fluidsynth audio and audio output
aSigL, aSigR fluidOut giEngine ; read all audio from soundfont
outs aSigL, aSigR ; send audio to outputs
endin
</CsInstruments>
<CsScore>
i 99 0 3600 ; audio output instrument also keeps performance going
e
</CsScore>
<CsoundSynthesizer>
Midi file input can be combined with other Csound inputs from the score or from live midi and also bear in mind that a midi file doesn't need to contain midi note events, it could instead contain, for example, a sequence of controller data used to automate parameters of effects during a live performance.
Rather than to directly play back a midi file using Csound instruments it might be useful to import midi note events as a standard Csound score. This way events could be edited within the Csound editor or several scores could be combined. The following example takes a midi file as input and outputs standard Csound .sco files of the events contained therein. For convenience each midi channel is output to a separate .sco file, therefore up to 16 .sco files will be created. Multiple .sco files can be later recombined by using #include... statements or simply by using copy and paste.
The only tricky aspect of this example is that note-ons followed by note-offs need to be sensed and calculated as p3 duration values. This is implemented by sensing the note-off by using the release opcode and at that moment triggering a note in another instrument with the required score data. It is this second instrument that is responsible for writing this data to a score file. Midi channels are rendered as p1 values, midi note numbers as p4 and velocity values as p5.
EXAMPLE 07D02_MidiToScore.csd
<CsoundSynthesizer>
<CsOptions>
; enter name of input midi file
-F InputMidiFile.mid
</CsOptions>
<CsInstruments>
; Example by Iain McCurdy
;ksmps needs to be 10 to ensure accurate rendering of timings
ksmps = 10
massign 0,1
instr 1
iChan midichn
iCps cpsmidi ; read pitch in frequency from midi notes
iVel veloc 0, 127 ; read in velocity from midi notes
kDur timeinsts ; running total of duration of this note
kRelease release ; sense when note is ending
if kRelease=1 then ; if note is about to end
; p1 p2 p3 p4 p5 p6
event "i", 2, 0, kDur, iChan, iCps, iVel ; send full note data to instr 2
endif
endin
instr 2
iDur = p3
iChan = p4
iCps = p5
iVel = p6
iStartTime times ; read current time since the start of performance
; form file name for this channel (1-16) as a string variable
SFileName sprintf "Channel%d.sco",iChan
; write a line to the score for this channel's .sco file
fprints SFileName, "i%d\t%f\t%f\t%f\t%d\n",\
iChan,iStartTime-iDur,iDur,iCps,iVel
endin
</CsInstruments>
<CsScore>
f 0 480 ; ensure this duration is as long or longer that duration of midi file
e
</CsScore>
</CsoundSynthesizer>
The example above ignores continuous controller data, pitch bend and aftertouch. The second example on the page in the Csound Manual for the opcode fprintks renders all midi data to a score file.