On Wed, 2012-08-22 at 00:11 +0200, Nick Copeland wrote:
Subject: Re:
[LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO)
From: d(a)drobilla.net
To: nickycopeland(a)hotmail.com
CC: jef(a)synthedit.com; linux-audio-dev(a)lists.linuxaudio.org
Date: Tue, 21 Aug 2012 16:59:03 -0400
Yes, but as already mentioned, for a modular to be usable a standard
is
required. The analog synths on which this was
modeled have such a
standard. As it turns out, that was based around A as well, just dug
up
by Robin Gareus on IRC:
https://en.wikipedia.org/wiki/CV/Gate
Even volts on A in both schemes.
That is a nice page but it definitely does not advocate any attachment
of
semantics (eg, frequency) to any specific voltage. It gives some
tables making
voltage comparisons between V/O and H/V using integral values however
these are given as examples of the translations between the two
systems
based on the preconfigured generation of a given frequency by an osc.
It clearly shoes a mapping between volts and absolute frequencies. That
there is tuning involved which can modulate the center slightly doesn't
matter. The plugins in question also have frequency modulation inputs
that can be used for tuning.
In the synthesizer as it is working, a voltage is representing an
absolute frequency. This is inevitable, because... well, you need to
represent an absolute frequency with a voltage when all you have is
voltage to convey information. You are correct that it is not set in
stone, but it is representing an absolute frequency regardless.
Fact: In a real-life genuine analogue Moog, even volts are A, e.g. 4V is
A4, or 440Hz +/- tuning.
How about a diagram:
note.frequency_out ------A------> osc.frequency_in
There are 2 possible scenarios here:
1) A carries a representation of an absolute frequency, and both "note"
and "osc" agree on what that representation is
2) Your synthesizer does not work
It doesn't matter, or even really make sense, to argue about where the
semantics of the signal on A "came from". They are there.
-dr