Let's Design and Build a (mostly) Digital Theremin!

"Where is MIDI vloc threshold detection on the drawing before and after the change ?"  - Mr_Dham

For both MIDI:vloc is sensed at the output of the KNEE block, though before the change the knee was independent of velocity, and after the change velocity is in-line and before the knee.  I tested the note-on velocity and that seemed to be working OK with the percussive DX Rhodes presets in Yoshimi, but I haven't checked non-percussive presets with CC modulations yet.

[EDIT] Ah, scratch that, before the change MIDI:vloc was located at the point where the velocity and knee outputs were combined via addition.  In other words, in both cases MIDI:vloc is sensed at the input of the envelope generator.

My intuition was the non edited version of your previous post. But my intuition was wrong too.

Perhaps what is surprising is the "negative velocity". 

It works very well with percussive sounds. 
We might need to tweak vloc thresholds with pads and drone sounds layered with D-Lev sounds: we don't want to trigger a Note-On with each expressive movement of left hand so vloc should be below the playing volume range (velocity impact included). Nothing we can't handle.

Maybe one thing to look at is this negative velocity and "damp" interaction at D-Lev sounds' side.

"Perhaps what is surprising is the "negative velocity".  It works very well with percussive sounds. "  - Mr_Dham

I agree, it allows one to abruptly play and then abruptly silence.  Bidirectional velocity was suggested to me lately by Lydia's husband George Pavlov, and has been eluding me until now.

"We might need to tweak vloc thresholds with pads and drone sounds layered with D-Lev sounds: we don't want to trigger a Note-On with each expressive movement of left hand so vloc should be below the playing volume range (velocity impact included). Nothing we can't handle."

I do see what you're saying.  I've been updating the manual, and here are the before and after modulation pick-off points:

"Maybe one thing to look at is this negative velocity and "damp" interaction at D-Lev sounds' side."

By this, are you are talking about damping the envelope generator and filters (VOLUME:damp & dloc) or unintentional throttling / retriggering of the MIDI sounds due to the bidirectional velocity?  The dloc pick-off point hasn't changed.

I could make the VOLUME:velo knob +/- (I already have a knob type for this) and use that to rectify the velocity?  So maybe positive velo would be positive velocity only, and negative velo would give bidirectional velocity.  This would give backward compatibility with the presets, though I think that bidirectional should probably be the new default (i.e. selected via positive velo) because it seems to be a general improvement?

What are your thoughts?  I very much appreciate your testing and comments, they are very constructive!

[EDIT] Vincent, here's a SW load that does bidirectional for positive velo and rectified for negative velo, please see if that's an improvement for drone scenarios: https://d-lev.com/support/80b55fde.zip

Another possibility might be to move the MIDI pick-off points earlier in the chain, like dloc, but that might be a little confusing because they wouldn't correspond to actual volume?

"Maybe one thing to look at is this negative velocity and "damp" interaction at D-Lev sounds' side."

"By this, are you are talking about damping the envelope generator and filters (VOLUME:damp & dloc) or unintentional throttling / retriggering of the MIDI sounds due to the bidirectional velocity?  The dloc pick-off point hasn't changed."

I was speaking about damping enveloper generator, but looking at it closer, dloc is at the right place and it works well.

Effectively, my real problem is throttling / retriggering of MIDI sounds. We may or may not want this synchronisation of D-Lev and MIDI attacks, so I would not change v-loc and c-loc place. https://d-lev.com/support/80b55fde.zip with VOLUME:velo knob +/- does the trick quite well. I would go for this solution. 

"... VOLUME:velo knob +/- does the trick quite well. I would go for this solution."  - Mr_Dham

Thank you Vincent, we'll go with that then - your input has been invaluable to this project!

AM/FM

Been messing with ring modulation (4 quadrant AM) a bit, it's pretty simple to just multiply DSP signals when you have a numeric multiplier in your CPU. It's more interesting I think when one of the signals is fixed and the other is variable. Here's me twiddling the D-Lev knobs: 

https://d-lev.com/audio/2023-09-21_ring_mod.mp3
https://d-lev.com/audio/2023-09-21_ring_mod2.mp3

I don't quite know what to make of these sorts of sounds. The preset list is (perhaps unfortunately) chock full of them, and they're fun to mess around with, at least for a bit, but at the end of the day are they really all that useful? I think I'm partially attracted to them just because they show off the extremes of the synth, which doesn't exactly justify their existence, much less their prevalence.  Then again, extreme synth is a thing.

Opinions?

For promotional purposes, as a demonstration of capabilities. Also, there are genres of music (noise music for ex. ) where such the sound is in demand.

BTW, the TW member Martel is a fan of that genre.

'Then again, extreme synth is a thing' - dewster

Is that like extreme ironing 

Most thereminist want voices, strings, trumpets, classic theremins, ... 

That said, having the possibility to do some extreme synthesis with the D-Lev is an interesting feature. It could be a part of theremin's sound vocabulary and one may want to put such a sound at a specific moment in a music piece. 

Maybe it is just a question of ordering them. We have 250 slots. There could be a place for
   Default presets for playing the theremin just after unboxing (voices, strings, trumpets, classic theremins, ... )
   Default preset for demonstrating instrument capability (extreme synthesis, noises, ...)
   Empty space for banks of sounds (e.g. animals.bnk, sci-fi.bnk, violins.bnk, ... ) and personnal creations

"For promotional purposes, as a demonstration of capabilities. Also, there are genres of music (noise music for ex. ) where such the sound is in demand."  - ILYA

So true.

"... having the possibility to do some extreme synthesis with the D-Lev is an interesting feature. It could be a part of theremin's sound vocabulary and one may want to put such a sound at a specific moment in a music piece."  - Mr_Dham

Yes.  I guess I'm worried about polluting the preset space (more than it already is!) with lame sounds.  Though I suppose if/when there are plenty to choose from the bad ones can be culled, so it's more of a short term problem of turning folks off with piles of presets they'll never use.

And I'm trying to figure out if this ring modulation approach is a keeper or not.  It started out as a simple multiplication:

  osc_0 * (osc_1 + osc_2)

But it turns out that ring modulation isn't all that interesting when all of the inputs track each other pitch-wise.  So the current approach is to use the above formula, but make osc_1 and osc_2 a fixed pitch of A440, which of course can already be offset from osc_0 and each other in a variety of ways, have FM applied, etc.  It's the A440 thing that feels like a bit of a kludge, but it does work, and I can't come up with an alternative.

[EDIT] Here's the SW load and some AM presets to demo it if anyone is interested: https://d-lev.com/support/5cae99d5.zip

[EDIT2] A demo of those presets: https://d-lev.com/audio/2023-09-25_am_0-7.mp3