Missing something in understanding the phase argument in SinOsc.kr

Questions
1

While working through Eli Fieldsteel’s book “SuperCollider for the Creative Musician” I am working on my own little experiment with Code Example 2.13: Use of “range” to specifiy custom output boundaries of a UGen

Here is my code:

(
x = {
	var sig1,sig2,lfo;
	sig1 = PinkNoise.ar(mul:1,add:0.5);
	sig2 = PinkNoise.ar(mul:0.5,add:0.5);
	lfo = SinOsc.kr(0.2,3pi/2).range(0,0.8); // not enough amplitude with 0,0.2
	sig1 = sig1*lfo;
	sig2 = sig2*lfo;
	sig1 = [sig1,sig2];
}.scope(2);
)
x.release(2);

It works fine but I find myself really digging in to these programming languages these days to understand what it going on. It is taking longer but I am enjoying it. So, my problem is that I am thinking that using the unit circle as a reference, if the phase in the SinOsc.kr is 3pi/2, why does pi/2 give an immediate loud noise when 3pi/2 starts from the 0 on the y-axis? Should the same thing 180 degrees out of phase not produce the same result? I am sure I am missing something simple.

2

with the .range method, you are mapping [-1,1] to [0, 0.8].
so
sin(3pi/2) = -1 maps to 0;
sin(pi/2) = 1 maps to 0.8
That’s all there is to it… I guess some audio phase talk (as in, “180 degrees out of phase would produce [roughly] the same result”) is with bipolar signals in mind; but because this is supposed to be an amplitude lfo you made it unipolar… so in that case that particular piece of phase wisdom doesn’t apply.

3

Thanks a lot. That was fairly simple but I was not getting why. This problem had made its way into my new “topics I do not understand in SC - to be investigated later” file. I saw a similar problem with Koala Sampler on fb today where somebody was not understanding why their sample was producing a click when their bass sample was released before the end of the sample and the signal was still high in amplitude. I say it is being too close to the problem.

4

To get a better understanding of this, I had to work through the other multiple of 0.5pi where I would get a zero amplitude for the output signals → 7pi/2. I do not really like working with radians. Maybe I will get used to it.