[sdiy] Linear FM concept again

[Scott Gravenhorst]

What exactly is linear FM used for?  I'm trying to wrap my
head around this, but my brain is being stubborn.

Here's how I understand it (which may be the whole problem):

In a very simple example, linear FM seems usually
implemented by mixing a modulating signal such as another
VCO with a VCO's linear pitch CV input.  If the modulating
signal is of a constant amplitude, the effect on the
modulated VCO's output is to more widely change the pitch at
lower CVs.  When I use an LFO to modulate pitch, I usually
want the modulation in terms of cents to be the same, which
won't happen if the LFO is mixed with linear pitch CV.  (it
does work with an expo input)

Why is this a good thing?

Why wouldn't one want to FM into the expo input?

I want to build some FM stuff for a linear synth, but not
understanding this is getting in the way of my design.

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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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