Csound Tutorial 5

After our first four tutorials, we can now create our own personal synthesizer where the pitch, amplitude envelope, and timbre can be altered in the score. Now I know what you are thinking, “Sequencing a melody is kool and all, but what if I was able to play it in real time, with a real MIDI controller…”.

Well, luckily for us, this is quite easy to achieve! Firstly, with your MIDI keyboard connected, in CsoundQT go to Configure and select your MIDI input interface (for a comprehensive introduction to MIDI see here). 

If you do not have a MIDI keyboard, then you can instead use the Virtual Keyboard by enabling it via Configure as follows

or using the CSOption -+rtmidi=virtual -Ma

Now taking our previous patch from Tutorial 4, we can modify it as follows to thus create a real-time playable synth.

<CsoundSynthesizer>

<CsOptions>
-Ma						;accept MIDI input on all channels
;-+rtmidi=virtual -Ma				;use if virtual unstable through GUI
</CsOptions>

<CsInstruments>
	sr     = 44100				;sample rate
	kr     = 4410				;control signal rate
	ksmps  = 10				;samples per control signal
	nchnls = 1				;number of output channels

	instr 1
iFreq	cpsmidi					;convert input MIDI frequency
iAmp 	ampmidi 10000				;scale input MIDI amplitude
a1	oscil	iAmp, iFreq, 1			;uses function table 1
a2	oscil	iAmp, iFreq, 2 			;uses function table 2
	out 0.6*a1 + 0.4*a2			;summed output
	endin

</CsInstruments>

<CsScore>

	;fn 	time 	size 	gen 	parameters
	f1 	0 	4096 	10 	1                                               ;sine
	f2 	0 	4096 	10 	1 0.5 0.3 0.25 0.2 0.167 0.14 0.125 .111 	;sawtooth
	f3 	0 	4096 	10 	1 0   0.3 0    0.2 0     0.14 0     .111 	;square
	f4 	0 	4096	10 	1 1   1   1    0.7 0.5   0.3  0.1 		;pulse

	e 30   ;score lasts for 30 seconds
</CsScore>

</CsoundSynthesizer>

So basically here instead of using variables p4 and p5 from the score as amplitude and frequency for the synth, we are using the input MIDI note’s velocity and pitch. NOTE: Our real-time synth is still dependent upon a score, i.e. execution time. Here we have selected 30s. This could also be archived by calling instr 1 for a certain period of time as follows:

;ins  strt  dur(p3)
i1    0     3600

In this fifth tutorial, we have learned how to break free from the static store and implement a real-time synthesizer. In the next tutorial we will investigate implementing audio effects for our synth.