FM on NerdSEQ: Is it FM or PM?

[mgd]

In the process of becoming more familiar with NerdSEQ's FM engine I would like to understand whether it is FM or actually PM (phase modulation).

The difference as far as I understand it is this:
  PM(t) = a*sin( f  * t + b * sin(f' * t))
  FM(t) = a*sin( (f + b * sin(f' * t)) * t)

For two operators this is pretty much the same but it will become different with three or more operators in a row.

Just curious

Kind regards,
Michael

[XORadmin]

It is FM, though I am not calculating every sample like this.