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<pre>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.<font face="Tahoma"><span style="white-space: normal;">
</span></font></pre><div><div> </div><div>Aren't there a couple of misconceptions here or at least some potential</div><div>for incompatibility?</div><div><br></div><div>The signal itself is a digital representation of a voltage modifier. The</div><div>voltage has no semantic other than its value, it does not represent freq</div><div>or gain or cutoff or anything - the semantics of what happens only occurs</div><div>at the 'sink/dst' of the signal.</div><div><br></div><div>Consider the following points:</div><div><br></div><div>a. 1/Oct is not a reference value, it is a definition for the effects of a</div><div>modifier signal. The value of 0.0 should definitely not refer to A440.</div><div>When a mod signal is applied to an osc then it modifies the setting</div><div>of the osc. You set the osc to A440 and apply 0v then it has no affect.</div><div>If you apply 1v it should output A880, that is 1/octave. If you want the</div><div>signal to be able to reduce the frequency then you transpose the osc down</div><div>by a couple of octaves and then set the base mod signal at 2+ve to get</div><div>back to a natural tuning, you can now reduce the frequence by 1/Octave too.</div><div><br></div><div>Now let's have a look at those negative values with another example:</div><div><br></div><div>b. It should not support negative values. Let's forget about the 1/Oct</div><div>for a minute. This defines how a mod signal is applied: if it is applied</div><div>to an osc or filter coff it represents 1/Octave. It can also be applied to</div><div>an amplifier though. If you accept negative values you will get phase</div><div>inversion and a relative signal gain, that is probably not the intention</div><div>of the modifier though: if you do not restrict the signal to +ve values</div><div>then the source of the mod signal may need to understand more about</div><div>the semantics of the sink - in the case that you have 0.0 to represent </div><div>A440 then does it also have to represent 0dB (or -96dB) when it</div><div>is applied to an amplifier for example. This is excessive since in an</div><div>arbitrary system where rewiring is possible then sources can be audio</div><div>signals or can be mod signals so now they need to understand where </div><div>they <span style="font-size: 10pt; ">are patched to be able to deliver a correct reference. That is at</span></div><div><span style="font-size: 10pt; ">best difficult and at worst unmanageable.</span></div><div><br></div><div>The above is partially opinion but is based on analogue signal paths</div><div>from the old mono/mega synths. Agreed it might be time to move on but</div><div>either way, a modifier signal of 1/Oct is based on the 1v/Oct and in</div><div>that model the modifier signal has no reference regarding frequency,</div><div>gain or anything else, that reference is a function of what it is being</div><div>used to modified.</div><div><br></div><div>Just to be complete, I have no objection to such signals having some</div><div>implied semantics. There will be some apps that do not have such</div><div>restrictions and this will result in inconsistencies - this is a good </div><div>thing though, probably, modifier signals and arbitrary routing was</div><div>always used as a testbed to generate new sounds so bring them on.</div><div><br></div><div>Regards, nick</div><div><br></div><div>"I had to enter a password that needed eight characters. I used "Snow</div><div>White and the Seven Dwarves",' Vine, 2011 Edinburgh Fringe (I think).</div></div><div><br></div> </div></body>
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