[PD] phasor to square

Andy Farnell padawan12 at obiwannabe.co.uk
Tue Jan 22 01:25:49 CET 2008

On Tue, 22 Jan 2008 00:46:18 +0100
"raul diaz" <raul.lete at gmail.com> wrote:

> Hi Andy, all!
> FOF (formante onde function) is an additive method that uses a periodic
> > impulse and a bank of tuned resonant filters as exponential sinewave
> > generators,
> >
> When you says "bank of tuned resonant filters" are you talk about the
> spectral effects produces by the FOF envelope, am I wrong?

No, not the envelope, as far as I know. I see at least two implementations of
FOF. The first comes from the CHANT vosim (Rodet) which uses stored table
oscillators (sines) and an exponential decay envelope. It can layer many of these
together to create a single grain. Vercoe and Clarke both wrote different Csound
implementations, the cool thing about one was that you could put anything you like
(non-sine) into the wavetable at i-time to get crazy voices, and the other computed
the sines so was less flexible but needed no memory.

The other implementation I am aware of is Cooks (which I presume is in the STK)
and uses parallel resonant filters. If you hit a highly resonant filter with an
impulse it rings, so behaves like an exponential decay envelope on a sine wave.

Same method, similar algorithm, different implementations.
It's essentially additive/parallel.

VOSIM (Kaegi) and PAF (Puckette) are two implementations of a totally different
method, which is basically AM to add sidebands to a sine. The modulation comes
from a raised window, usually Gaussian, narrowing the window effectively increases
the modulator frequency and the position of two sidebands.

It's a while since I read anything about these and there are several 
implementations so I may be way off. In theory (and no doubt someones done it) you
can do the same with FM and modulate the frequency of the packet.

> Or maybe are you talking about a different implementation from the original
> one by Rodet.
> I would know your suggestions about Pd implementation of FOF synthesis.
> Saludos!
> -- 
> Raul Diaz Poblete
> *************************
> raul.lete at gmail.com
> Barcelona [Spain]

Use the source

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