Sound differences SAPF - SC

[fellipemartins]

Thanks a lot!

I tried the FM PM conversion formulas with no good equivalent results.

Frequency Modulation – Phase Modulation – Delay Modulation (FM / PM / DM)

Thinking again about these basic synthesis strategies, I wanted to see how to write them in equivalent ways in SC. Phase modulation is roughly the same as frequency modulation: it produces sidebands in the same way, and this is also the case for delay modulation. Delay modulation is practical because it enables FM-like modulation without knowing the source’s frequencies. Definitions: carr: carrier frequency mod: modulator frequency dev: deviation, maximum change of carrier index = dev / mod …

{SinOsc.ar(0, (220 + (SinOsc.ar(110) * SinOsc.ar(0.1, -0.25).range(0,10))).mod(2pi) )/2}.play

(
{
	var carr = 220;
	var mod = 110;
	var index = SinOsc.ar(0.1).range(0,10);
	var phi = ((1 - SinOsc.ar(mod, pi/2)) * index);
	SinOsc.ar(carr, phi.mod(2pi))/4
}.play;
)

Here is the SAPF recording:

And here is how they sound like in SC:

There is some kind of wobbling in the SAPF version which I am not able to reproduce…

@jamshark70

In sapf, in the source code, there’s phase(sc_wrap(iphase, 0., 1.) * kTwoPi) which suggests the phase input might go 0 to 1 instead of 2pi. So the intensity of the modulation would be 2pi times more intense. But I’m not sure if that wrap(0., 1.) * 2pi really means what I think it does.

I also could not properly find where in SAPF the ranges were defined, neither what would be the difference between an lfo and a sinosc…

The closest I could get was inserting a modulo operation to 1 and then scaling to [-8pi, +8pi]

{SinOsc.ar(0, ((220 + (SinOsc.ar(110) * SinOsc.ar(0.1, 3pi/2).range(0,10))).mod(1)).range(-8pi,8pi) )/2}.play