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

Sean Bolton sean at smbolton.com
Mon Aug 20 05:25:34 UTC 2012

Hi Dave,

On Mon, 20 Aug 2012 00:27:12 -0400 David Robillard <d at drobilla.net>
> I am porting to LV2 some AMS-influenced plugins (mainly those by Fons)
> which have odd 1/Oct frequency ports.  I understand why it is
> sometimes convenient to use octaves rather than the more typical Hz
> for frequency, but after some digging to figure out how to precisely
> describe this unit, I discovered the central frequency is middle C,
> i.e. C4, i.e. around 262Hz.

I know that most of the 1/octave ports in these plugins describe
*intervals* rather than *frequencies*, that is, they describe frequency
ratios relative to bases usually specified by other ports.

Are you saying that there are some 1/octave ports which
are actually used to describe absolute frequencies, independently
of other input? If so, that is odd, as you said.  But to address your
question, any "standard" for 0.0 = X Hz is going to be arbitrary,
whether it is ~261.625Hz or 440Hz or even 415Hz for the baroque
folks. If you're proposing something that asks plugin authors to
"fix" their plugins to the standard, why not just ask them to be clear
about whether a port specifies an interval or an absolute frequency, and
if it's an absolute frequency, use the more typical Hz port type?


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