My synth's curve argument has no effect

Questions Code Review
1

I wanted to have a synth defined where I can pass in the curve shape as an argument:

(
SynthDef(\syn, {
	arg cv;
	Out.ar([0,1],
		SinOsc.ar(
			mul: EnvGen.kr(Env([0, 0.1, 0], curve: cv),
				doneAction: 2
			)
	))
}
).add;
)

// but playing it sounds like a sine curve shape
Synth(\syn, [\cv, \step]) // Why?

What is wrong with this code snippet for passing the curve shape as an arg?

2

This is, yet another, example where using NamedControl or \cv.kr is far superior.

Rather than doing…

SynthDef(\syn, { arg cv; ... });

If you had used named control with a default value…

SynthDef(\syn, {
   \cv.kr(\lin);  // or NamedControl.kr(\cv, \lin);
}).add;

…you would have immediately been greeted with an error.
The issue is that you cannot send a symbol to a synth. Synth Controls are much more like Buses (In in particular) than they are like function arguments, and can therefore, only accept floating point numbers, or arrays thereof.

3

The easiest way might be just to send the whole envelope:

(
SynthDef(\syn, {
    var env = \env.kr(Env([0, 0.1, 0], curve: \sin).asArray);
    Out.ar([0, 1],
        SinOsc.ar(mul: EnvGen.kr(env, doneAction: 2))
    );
}
).add;
)

Synth(\syn);
Synth(\syn, [\env, Env([0, 0.1, 0], curve: \step)]);

(The “curve” parameter gets translated into two values to be sent to the server:

Env([0, 0.1, 0]).asArray
Env([0, 0.1, 0], curve: \exp).asArray
Env([0, 0.1, 0], curve: 1).asArray

so you could do something more complicated to only send the curve values, here is how they are calculated:

f = { |cv| 
  [Env.shapeNumber(cv), Env().curveValue(cv)]
};

then you could recieve this array in your synth and inject it appropriately into the env array…)

3 Likes