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

Fons Adriaensen fons at linuxaudio.org
Thu Aug 23 10:56:29 UTC 2012

On Wed, Aug 22, 2012 at 05:32:26PM -0400, David Robillard wrote:

> The oscillators actually have three CV frequency ports: frequency, lin.
> FM, exp. FM.  Since the FM ports provide the ability to modulate in a
> moogey way, I'm thinking perhaps the ideal solution (outside AMS) is to
> simply make the frequency port Hz and leave the others as-is.  The
> others, being FM, are purely relative.

(upper case names refer to the enums in *.h, CV means audio rate in AMS)

FREQ (CV, log) : keyboard voltage, so this needs to be log in AMS.

OCTN, TUNE (control, log) : from GUI. In fact one control separated into
and 'octave' switch and 'tune' slider. They are two ports only because
AMS derives the GUI from the plugin interface. Today I'd separate them
only in the GUI.

Note that there is no problem at all if the for example the VCO has
middle C as the reference and the keyboard has A440. Just use the
'TUNE' control to shift everything by 3/4 octave. That's one of
the reasons why it exists.

> The filters are slightly different: they also have two CV FM ports (lin
> and exp), but the cutoff frequency is a control port (not CV).  It might
> be nice to make this CV as well, space be damned.  This one port could
> also be Hz, leaving the others alone.

Sorry but this is wrong. The filters have:

A_FREQ (CV, log) : keyboard voltage),
C_FREQ (control, log) : GUI slider 
A_FMOD (CV, log) : modulation (e.g. envelope), gain set by C_FMODG (slider).

So the 'cutoff' is avaiable as both CV and control, and they don't
have linear modulation. 



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