How to make FM stacks

[Chris-S]

Hi,
concerning the docs it should be possible to create FM stacks with Zyn.
But I didn't figured out yet how to do it.

So, how to use the external modulator settings to create for example
a C(1)-M(4)-M(2) stack?

Meaning: a freq-ratio 2 modulator modulating a ratio 4 mod modulating the ratio 1 carrier.

[Chris-S]

Ok, I think it should go this way:

We need two voices, voice 1 will be the top of the stack.
Set Octave=2 for the modulator and Octave=3 for
the main oscillator.

The amplitude of this voice will be zero and in voice 2
we use the External mod. = ExtMod 1. This is the
carrier of our stack.

Don't forget to bypass the filters to get real FM sounds.

[jackoo]

thanks for the info.
I guess I ought to try doing stuff like that...

[Chris-S]

I tried to rebuild a classic FM sound consisting of two 3op stacks but it does not come close to the original. So either something is wrong with my settings or
Zyn can not simulate FM stacks well.

[Chris-S]

So either something is wrong with my settings or
Zyn can not simulate FM stacks well.

Ha, found the reason. "Real" FM synths like the DX7 don't use FM but PM (phase modulation). So in ZYN one should use PM and not FM as modulator setting.

[Chris-S]

Hi,

For FM sounds the operators frequencies are called ratio.

For example: When a modulator has double frequency compared to the carrier the ratio is 2.

The following list shows a mapping from the FM ratio
to the ZYN modulator frequency setting.

Code: Select all

     Ratio       Oct. Coarse Det.  Fine Det.
---------- ---------- ----------- ----------
       0.1         -3          -8     13.686
      0.25         -2           0      0.000
       0.5         -1           0      0.000
   0.66667         -1          10     -1.954
      0.75          0         -10      1.954
       1.0          0           0      0.000
       1.5          1         -10      1.954
       2.0          1           0      0.000
       2.5          1           8    -13.686
       3.0          2         -10      1.954
       3.5          2          -5     18.826
       4.0          2           0      0.000
       4.5          2           4      3.910
       5.0          2           8    -13.686
       5.5          2          11      1.319
       6.0          3         -10      1.954
       7.0          3          -5     18.826
       8.0          3           0      0.000
       9.0          3           4      3.910
      10.0          3           8    -13.686
      11.0          3          11      1.319
      12.0          4         -10      1.954
      13.0          4          -7     -9.473
      14.0          4          -5     18.826
      15.0          4          -2    -11.731
      16.0          4           0      0.000
      17.0          4           2      4.956
      18.0          4           4      3.910
      19.0          4           6     -2.487
      20.0          4           8    -13.686

[ishkabbible]

thanks for the info.
I guess I ought to try doing stuff like that...

I have been experimenting with this for a couple months now in 496 - it is how I got some of the odd sounds in "Buchlava in C++". It seems to work well most of the time, but occasionally something goes sideways and it crashes the plugin container in Reaper (never when playing, only when adjusting controls, so I assume it is a threading issue)

The following list shows a mapping from the FM ratio
to the ZYN modulator frequency setting.

Thanks! Excellent info. <runs off to play>

[Chris-S]

I tried to rebuild a classic FM sound consisting of two 3op stacks

You can download this patch now on the ZYN banks&patches page.
It's called Stratotron and is one of my favorite DX7 sounds.