[PD] oscillators (osc~ / cycle~) not working well in FM?

Alexandre Torres Porres porres at gmail.com
Sat Nov 21 17:06:51 CET 2015

By the way, I was wondering and thinking if this was a particularity of the
"0Hz carrier FM", that is: a FM patch with no carrier frequency. But I
tried other regular FM patches with a carrier signal and could see that it
didn't keep static as well.

On the other hand, the same patch implemented as Phase Modulation (PM)
maintains a static waveform in Pd.

In my last example, the patch I had as "waveshaping" could be thought of as
a "0hz PM" patch.

Now, I tested the PM stability with the [phasor~] + [cos~] architecture and
also with [cycle~].

The FM instability happened with both [osc~] and [cycle~].

In Max, a FM patch with [cycle~] is stable.

In short, there's something fishy with FM in Pd...


2015-11-21 13:25 GMT-02:00 Alexandre Torres Porres <porres at gmail.com>:

> > Can you elaborate?
> Not easily I'm afraid, so I'll try to keep it simple: it's a
> demonstration on the relationship between FM and waveshaping, compare now
> both patches in my new example. The waveshaping does not change through
> time.
> But let me attempt to reason why it should keep static - it's like any
> other FM patch, once you have set the parameters, the waveform must be
> static and not change in time. My tests with supercollider and Max had a
> good result (waveform kept static). I also tried in Pd with cycle~ and in
> the newest vanilla.
> cheers
> 2015-11-21 11:26 GMT-02:00 Roman Haefeli <reduzent at gmail.com>:
>> On Sat, 2015-11-21 at 02:59 -0200, Alexandre Torres Porres wrote:
>> > howdy, attached there's a patch where I was experimenting with FM
>> >
>> >
>> > the waveform shouldn't change with time, but it does. Give it a while
>> > though, 30 seconds is enough to hear a change in tone quality, then
>> > resseting the oscillator phase brings it back to where it was
>> >
>> >
>> > don't know why it does come out of phase, an equivalent patch in SC
>> > and Max does not get out of phase...
>> I hear and see what you mean. Interesting question. Frankly, I don't
>> quite understand why it is expected to stay in phase. Can you elaborate?
>> Roman
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