[LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO)

David Robillard d at drobilla.net
Tue Aug 21 00:50:38 UTC 2012

On Tue, 2012-08-21 at 11:02 +1200, Jeff McClintock wrote:
> > I think the most reasonable standard for an absolute 1/oct
> > frequency unit is 0.0 = 440Hz
> My modular plugins use a reference of 440Hz. Also parameters are ranged
> between 0.0 - 10.0 but can exceed that if need be. (in a modular synth,
> everything needs to interoperate).
> So for frequency 5.0 is 440Hz (Middle-A). i.e. the middle of the range -
> 5.0, is the standard 'middle' key.

While I initially thought negative values was really weird, on second
thought having it centred about 0.0 is nicer, especially considering the
relative uses

> Great idea though. Octaves are far more universal than western semitones,
> yet trivial to convert between.

Yeah, in a modular octaves or Hz are really the only sane choices,
semitones would be nuts.  I'm not really all that sold on octaves since
Hz lacks this problem and the complexity of the math doesn't really
differ that much either way, but it's convenient in some ways.

> 440Hz is a good choice.

I agree.  I guess I will change the reference tone of the LV2 ports.
IMO the nearly universal 440Hz is a stronger convention to adhere to
than what is essentially "whatever the note module in AMS happened to
use", and though conservative plugin ports acting differently is
unfortunate, acting sensibly in a grander scheme of things is more

Though not based around 0.0, the fact that your plugins are somewhat
similar and tuned to a 440 reference is helpful.  If some day our (in
many ways extremely similar) modular visions should meet, I suppose
we'll have to sort that out :)



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