After looking at it I think probably you can but you need trig calculations every sample when you change the frequency and quite some additional calculations for the WGR every sample
in this case.
So its cheaper to use a standard oscillator with a sine aproximation for phase mod.  in both cases.

The MCF seems lighter on CPU then what I do if you insist that the rotation
must be on a perfect circle instead of the parapolic shape,
but I think when used as an oscillator it has issues
with frequency accuracy or amplitude rescaling or something similar?

And it appears not to rotate on a perfect circle internally either
but just from looking at the paper I can't tell if and how that matters.

I remember years ago I investigated both for use as an undamped oscillator and came to the conclusion that a fast sine approximation is superior for phase modulation.
But I dont recall the details.

The sine approximation I use only needs 4 multiplies so I am not sure
if I am on the right path using filters.

There seems to be an advantage with voice stealing though, the click
you get is masked and blurred by the filters response


Am 03.04.2018 um 14:37 schrieb Corey K:
Yes, I think you can do phase modulation with those filters. They are referred to colloquially as "phasor filters", because their phase is manipulated in order to rotate a vector around the complex plane...

On Tue, Apr 3, 2018 at 8:16 AM, gm <g...@voxangelica.net <mailto:g...@voxangelica.net>> wrote:


    Yes it's related, I dont recall if I used one of these filters
    in my first implementation which was several years ago.
    I used a complex filter before I used the SVF and AP.

    But I think you can't do full phase modulation with such filters?
    I think that was my motivation to apply the rotation outside of
    the filter.

    Either way it seems lighter on cpu when you use the external
    rotation with
    parabolas instead of trig operations since you dont have to constantly
    adapt the internal state of the filter.

    A drawback of the method in general with either filter is that
    you can cancel the internal state with an impulse.

    I havent figured out what the best excitation signal is.

    The paper you linked suggests to delay the impulse until a zero
    crossing
    but that is not an option in my use cases.


    Am 03.04.2018 um 01:46 schrieb Corey K:
    Your idea seems to bear a few similarities to this (just in case
    you haven't seen it already):
    https://ccrma.stanford.edu/~jos/smac03maxjos/
    <https://ccrma.stanford.edu/%7Ejos/smac03maxjos/>



    On Mon, Apr 2, 2018 at 2:46 PM, gm <g...@voxangelica.net
    <mailto:g...@voxangelica.net>> wrote:


        I don't know if this idea is new, I had it for some time but
        have never seen it mentioned anywhere:

        Use a filter with high q and rotate it's (complex) output by
        the (real) output
        of another filter to obtain a phase modulated sine wave.
        Excite with an impulse or impact signal.

        It's basically crossed between modal and phase modulation
        synthesis.

        Now there are some ideas to this to make it practical and a
        useful substitute for phase modulation and FM:

        You can use a state variable filter with an additional
        allpass instead of
        the complex filter to obtain a filter you can pitch modulate
        in audio
        (useful for drum synthesis ect) (or maybe the 90 shift can be
        designed more efficiently
        into the SVF IDK.)

        Instead of expensive trig calculations for the rotation, or using
        the normalized complex signal form the other filter (also
        expensive)
        just use a very coarse parabolic sine/cosine approximation
        and the real signal,
        the difference is really very small sonically, since the
        modulator is still sine
        and the radius stays around 1 so it's the effect of a small
        amplitude modulation on the modulator
        caused by the slight deviation of the circle.
        I couldnt tell the difference when I tested it first.

        You need 7 mults and 4 adds in addition to the SVF for the AP
        and rotation per carrier.

        But you save an envelope for each operator and have a pretty
        efficient sine operator with the SVF.
        And you get all the benfits of phase modulation over
        frequency modulation of the
        filter cutoff.
        It's very useful for drum synthesis but also useful for some
        other percussive sounds like "FM" pianos etc.

        Here is an audio demo, with cheap "soundboard" and some other
        fx added:
        https://soundcloud.com/traumlos_kalt/smoke-piano-test-1-01/s-W54wz
        <https://soundcloud.com/traumlos_kalt/smoke-piano-test-1-01/s-W54wz>

        I wonder if this idea is new?

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