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

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To: <d@...>, <fons@...>
Cc: linux-audio-dev@lists.linuxaudio.org <linux-audio-dev@...>
Date: Wednesday, August 22, 2012 - 1:24 am

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> 1) Fork these plugins and add a tuning frequency port=2C in Hz=2C which> =
makes the current reality of them using absolute octave signals go away.> T=
he avwlv2 project will have to adjust the ported AMS modules likewise.> Tho=
ugh your plugins do not currently do this=2C you now seem to think this> is=
the correct solution?> > 2) Define an absolute unit in octaves with a stan=
dard=2C absolute=2C center> frequency. This is current reality=2C except th=
e "define" part=2C and the> 'standard' is a weird frequency.
Not sure if I can really comment on these two options but can't you movetun=
ing into the MIDI code? Here is what I mean: > Suppose you have a VCO with =
two 1/octave control ports.> One is used by a GUI element=2C say a slider w=
hich could> have a scale in Hz=2C note names=2C or octaves. The second> is =
the 'voltage' from a keyboard.> > The actual frequency of the VCO would be>=
> F =3D exp2(V1 + V2 + C) (1)> > where C is some constant=2C e.g. =
log2(440).
The constant 'C' used to be the keyboard voltage from the resistordivider c=
ircuit. It was intended to be the voltage that would produceA440 on middle-=
A on an 8' transpose=2C no mods or detuning. It was neverthat accurate by w=
hich I mean the oscillator signal depended on otherenvironmental influences=
and is why many of the old beasts had an A440reference sine wave and globa=
l/auto tuning.
You could extract the same from your MIDI signal so that the MIDI inputis a=
lso converted into a port that is summed with the mods to producethe output=
signal - you are going to have summing=2C it is needed to linkkbd=2C mod=
=2C fine/rough tuning.

control inputs)=2C so this is equivalent to saying there should be two> por=
ts where only one is absolute.
Well=2C in the voltage controlled synths there were properties of anoscilla=
tor. If your synth does not have controls but only ports then howdo you sel=
ect the waveshaping code? How do you select 12+24dB/Oct filters=2Chow do yo=
u select keyboard tracking versus non-keyboard tracking oscillators=2Care t=
hese all input ports with implied semantics? Are they different modules?
There are other examples but when I was starting on Bristol this single iss=
uelead me to separate out mod/volt controls and property controls since the=
optionof using an input port to define a constant is a waste of CPU cycles=
and is alsogoing to be pretty arbitrary. I also liked the concept of it be=
ing 'fully bussed' but that truth is that it does not apply itself that wel=
l. Having separate modules for each waveform=2C filter type=2C tracking met=
hods=2C etc=2C is also a waste of time and even more so if different module=
s have to be invoked each time somebody changes parameters.
The other parameter that is going to be an issue is transpose. You couldloo=
k at this as another input port but that is another waste of CPU to havea p=
ort for a constant value. Also=2C the original synths did not have avoltage=
value that represented transpose=2C it was a property that adjustedthe rat=
e of the oscillator which drove the waveshaping circuits. The issuehere (wi=
th the originals) is that the waveshaping was dependent on thefrequency so =
if an oscillator is transposed then some changes may alsobe needed to the p=
arameters of the shaping circuit. This is difficult toemulate if you litera=
lly only have ports rather than properties/controls.It can be argued here t=
hat you are not intending to actually emulate anyspecific synth in which ca=
se these interactions are not necessary but ifyou are not emulating then wh=
y do you want V/Oct which is an emulation ofthe controls of the analogue sy=
nths?
Also=2C if you do want to use V/Oct then perhaps also get rid of -ve values=
.I mentioned this before and I always get ainsy when considering 'what if t=
hecontrol bus goes negative?' It is unanticipated results for an AMP and -v=
evalues to a filter cutoff can be=2C well=2C put it this way=2C I check for=
them.The Moog spec for CV was 0..10v=2C the value does change according to=
yoursources but it never included -ve volts.
Regards=2C nick.
=

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&gt=3B 1) Fork these plugins and add =
a tuning frequency port=2C in Hz=2C which&gt=3B makes the curren=
t reality of them using absolute octave signals go away.&gt=3B T=
he avwlv2 project will have to adjust the ported AMS modules likewise.&gt=3B Though your plugins do not currently do this=2C you now seem t=
o think this&gt=3B is the correct solution?&gt=3B&nbs=
p=3B&gt=3B 2) Define an absolute unit in octaves with a standard=
=2C absolute=2C center&gt=3B frequency. This is current reality=
=2C except the "define" part=2C and the&gt=3B 'standard' is a we=
ird frequency.Not sure if I can really comment on=
these two options but can't you movetuning into the MIDI code? =
Here is what I mean:&nbsp=3B&gt=3B Suppose you have a=
VCO with two 1/octave control ports.&gt=3B One is used by a GUI=
element=2C say a slider which could&gt=3B have a scale in Hz=2C=
note names=2C or octaves. The second&gt=3B is the 'voltage' fro=
m a keyboard.&gt=3B&nbsp=3B&gt=3B The actual frequenc=
y of the VCO would be&gt=3B&nbsp=3B&gt=3B &nbsp=3BF =
=3D exp2(V1 + V2 + C) &nbsp=3B &nbsp=3B &nbsp=3B &nbsp=3B(1)&gt=
=3B&nbsp=3B&gt=3B where C is some constant=2C e.g. log2(440).The constant 'C' used to be the keyboard voltage fro=
m the resistordivider circuit. It was intended to be the voltage=
that would produceA440 on middle-A on an 8' transpose=2C no mod=
s or detuning. It was neverthat accurate by which I mean the osc=
illator signal depended on otherenvironmental influences and is =
why many of the old beasts had an A440reference sine wave and gl=
obal/auto tuning.You could extract the same from =
your MIDI signal so that the MIDI inputis also converted into a =
port that is summed with the mods to producethe output signal - =
you are going to have summing=2C it is needed to linkkbd=2C mod=
=2C fine/rough tuning.&gt=3B There is no such thi=
ng as "property of the VCO" except parameters (i.e.&gt=3B contro=
l inputs)=2C so this is equivalent to saying there should be two=
&gt=3B ports where only one is absolute.Well=2C i=
n the voltage controlled synths there were properties of anoscil=
lator. If your synth does not have controls but only ports then howdo you select the waveshaping code? How do you select 12+24dB/Oct filter=
s=2Chow do you select keyboard tracking versus non-keyboard trac=
king oscillators=2Care these all input ports with implied semant=
ics? Are they different modules?There are other e=
xamples but when I was starting on Bristol this single issuelead=
me to separate out mod/volt controls and property controls since the optio=
nof using an input port to define a constant is a waste of CPU c=
ycles and is alsogoing to be pretty arbitrary. I also liked the =
concept of it being 'fully bussed' but&nbsp=3Bthat truth is that=
it does not apply itself that well. Having separate modules for&nbsp=3Beach waveform=2C filter&nbsp=3B=
type=2C tracking methods=2C etc=2C is also a waste of time and even&nbsp=3B=
more so if different&=
nbsp=3Bmodules have to be invoke=
d each time somebody changes&nbsp=3Bparameters.The other parame=
ter that is going to be an issue is transpose. You couldlook at =
this as another input port but that is another waste of CPU to havea port for a constant value. Also=2C the original synths did not have a<=
/div>voltage value that represented transpose=2C it was a property tha=
t adjustedthe rate of the oscillator which drove the waveshaping=
circuits. The issuehere (with the originals) is that the wavesh=
aping was dependent on thefrequency so if an oscillator is trans=
posed then some changes may alsobe needed to the parameters of t=
he shaping circuit. This is difficult toemulate if you literally=
only have ports rather than properties/controls.It can be argue=
d here that you are not intending to actually emulate anyspecifi=
c synth in which case these interactions are not necessary but ifyou are not emulating then why do you want V/Oct which is an emulation of<=
/div>the controls of the analogue synths?Als=
o=2C if you do want to use V/Oct then perhaps also get rid of -ve values.I mentioned this before and I always get ainsy when considering 'w=
hat if thecontrol bus goes negative?' It is unanticipated result=
s for an AMP and -vevalues to a filter cutoff can be=2C well=2C =
put it this way=2C I check for them.The Moog spec for CV was 0..=
10v=2C the value does change according to yoursources but it nev=
er included -ve volts.Regards=2C nick.=

=

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Messages in current thread:
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Jeff McClintock, (Mon Aug 20, 11:02 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Tue Aug 21, 12:50 am)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Nick Copeland, (Tue Aug 21, 8:14 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Fons Adriaensen, (Tue Aug 21, 9:54 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Tue Aug 21, 10:29 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Fons Adriaensen, (Tue Aug 21, 11:02 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Tue Aug 21, 11:50 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Thorsten Wilms, (Wed Aug 22, 8:30 am)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Wed Aug 22, 4:43 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Fons Adriaensen, (Wed Aug 22, 9:12 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Wed Aug 22, 9:32 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Fons Adriaensen, (Thu Aug 23, 10:56 am)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Thu Aug 23, 4:06 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Fons Adriaensen, (Thu Aug 23, 4:35 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Thu Aug 23, 5:07 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Wed Aug 22, 5:37 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Nick Copeland, (Wed Aug 22, 1:24 am)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Wed Aug 22, 1:57 am)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Tue Aug 21, 8:59 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Nick Copeland, (Tue Aug 21, 10:11 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), Jens M Andreasen, (Wed Aug 22, 3:50 pm)
Re: [LAD] Plugin 1/oct frequency controls (AMS/MCP/VCO), David Robillard, (Tue Aug 21, 10:52 pm)