[sdiy] FIlter FM=narrow band 2 quadrant spectrum modulation?

[Sean Costello]

Don't forget that modulating a 4 pole filter also results in phase
modulation, which is similar to true frequency modulation.

I would just call it Filter FM.

Sean Costello


----- Original Message ----- 
From: "karl dalen" <dalenkarl at yahoo.se>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, October 26, 2005 12:49 PM
Subject: [sdiy] FIlter FM=narrow band 2 quadrant spectrum modulation?


> I just relized im unshure!
>
> What are filter FM actually?
>
> The test:
>
> Lets modulate a 4 pole LP filter (resonance at zero)
> with a sine wave, and a saw wave as the inputsignal
> to the filter, by mowing the poles of the filter up and down,
> isnt this actually band limited AM? Or band selective AM!
> Or perhaps narrow band 2 quadrant spectrum modulation?
> (quite fancy naming) :-)
>
> Under what synthese label should this actually be placed?
> Can it be labeled?
>
> Should this be valid all the way up to self oscillation
> of the filter and then it be renamed Filter FM as usuall!
> (asuming that the input signal has been remowed).
>
> Lets say we do the same but now with hertz wide BP filter,
> all we would hear are a series of harmonics fading in and out,
> done rappidly wouldent that resemble more to oscillator FM soundwise?
> Using square wave as inputcarrier would be interesting, what would that
> resemble in ordinary oscillator FM? (since only odd harmonics are AM'ed!)
>
> KD