[sdiy] MIDI Velocity on analog synths

[rsdio at sounds.wa.com]

Grant,

I believe that it is common for all modulation patches to involve  
scaling, Offset might be useful as well, but you always have the  
original cutoff or resonance knob for the DC offset. I'm not  
surprised that 100% is pretty crazy. Yep, you'll want a scaling  
parameter (with proper multiply and truncate/round/dither as  
appropriate). You can have either a single scaling parameter and a  
destination selection (to choose between cutoff or resonance or maybe  
amplitude), or you could have a scaling parameter for each  
destination without any selection necessary (since a scale factor of  
0 would turn off the modulation).

While you're doing Note On Velocity, I say you might as well  
implement Note Off Velocity. You'll just need to implement a second  
set of scaling and routing parameters. Admittedly, very few  
controllers send Note Off Velocity. However, many more synths respond  
to Note Off Velocity, even if they don't generate the message from  
their own keyboard.

I agree that it would be rather difficult to make the Pro-One ADSR  
respond to CV directly. You could implement a parallel digital ADSR  
in the processor, and sum its output on the VCA CV input, but that  
might require alterations of the ADSR settings when the user makes a  
patch. Also, I'm not sure whether digital ADSR would perform very  
well with a small 8-bit.

In any event, glad to see you're still working on this thing!

Brian


On Feb 5, 2014, at 18:38, MTG wrote:
> Thanks all for the info. I coded up a test section and it works OK.  
> I guess I need to add a CC parameter for setting the depth or gain  
> or whatever you want to call it ... the amount velocity affects the  
> cutoff or resonance. Right now I have it basically 0 velocity is  
> zero CV and max velocity is max CV and that's pretty crazy.
>
> I haven't played around with connecting the DAC to the CEM3310  
> ADSR's as I only have one DAC channel left and no idea where it  
> would be useful/possible in the ADSR's.
>
> GB
>
> On 2/5/2014 6:02 PM, Andrew Simper wrote:
>> In the past I've handled the note on and note off velocities as
>> different modulation sources, you typically don't want to combine  
>> them
>> into a single source because of the problems mentioned in this  
>> thread.
>> Otherwise just keep the note on velocity and throw away the note off
>> velocity. If you are in charge of voicing duties you may also want to
>> keep a stack of previous note ons as well as note on velocities so  
>> you
>> can re-assign old voice notes and velocities when playing overlapped
>> then released notes.
>>
>> A good (but complicated) place to send the velocity is to scale the
>> envelope outputs using the attack time of the envelope to smooth the
>> scaling. This means you can adjust the snappiness of the filter or
>> amplitude response using the attack pot. If a dual pot is not an
>> option then you could add a single "velocity glide" pot to adjust the
>> smoothness of velocity response instead before sending that signal to
>> scale the envelopes.
>>
>> On 6 February 2014 02:11, MTG <grant at musictechnologiesgroup.com>  
>> wrote:
>>> I'm thinking of adding velocity as a CV parameter to the Pro One  
>>> and I'm wondering how this is typically done on other synths or  
>>> MID-CV converters since I have neither. I imagine when an Note-On  
>>> arrives you apply the velocity value (voltage) to VCF Cutoff or  
>>> Resonance or whatever, but have you noticed if the Note-Off or  
>>> Note-On with velocity of zero then zeroes the velocity CV?  Or  
>>> just leave the voltage where it is until the next Note-On?
>>>
>>> If you have any experience with this let me know...
>>>
>>> GB
>