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

[karl dalen]

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