@weightless, thank you so much to your patch! It finally shed some light on this whole FM/PM thing. Sorry, but lots of questions coming:

1. I spent half a day reading about FM/PM, but it's still not clear what's the fuzz is all about. If FM could be described with these equations:
   

And PM with these:

While phase and frequency are connected as following:

(Formulas were take from here: https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/RadCom/part12/page1.html)

Isn't it all the same?

I undersand that perhaps in 80's PM was easier to implement, But if math works essentialy the same in both ways, why do results differ?

2. In my patch I've used modulation index in range 0-14 as it is shown in Chowning's book (as it correspond to 0-99 of operator output for synth):

I notice, that for PM you are using modulation index in range 0-2 (200/100 right?) and it sounds exactly the same? Could you please explain those numbers?

Once again, thank you so much for your help!

Hi, everybody!

I'm trying get into FM synthesis. As an excercise I decided to recreate some of Yamaha DX7 algoritms in PD and compare results with Korg Volca FM, that is DX7-compatible.

I took FM patch for two operators from FLOSS manual, and extended it to 3 operators stack as shown here:

But resulting sound is much more harsh in comparison with the same patch on Volca. I don't understand what I'm doing wrong.
fm_mod_stack.pd

Thanks for any help in advance!