Probably just a simple question...

[fluffy_little_something]

I guess this is my virgin thread on the U-he forum, sorry Urs and don't waste too much time on it

Anyway, why is the C3 key audibly mute and why does the volume increase from that note in both directions on this patch I made in the demo version (cool by the way that one can save patches in the demo, especially if one ends up buying it)? It is just a slightly modified init patch.
I know this behavior from a few other synths I have used so far, and I don't know why. So I tried it in the Hive demo and found the same behavior when using a couple of key tracking -> volume modulations. Is there a simple explanation for a correct behavior or is the behavior somewhat illogical to begin with?

https://app.box.com/s/iymd1bw1r3valewgcesvfebxu0mmuy2u

[EvilDragon]

You used keyfollow twice in mod matrix, moreover applied it twice in each slot to the same destination. So, you quadrupled keyfollow on osc 1 volume...

[Chris-S]

The keyfollow is bi-directional and when the modulation value gets below zero the wave is multiplied by a negative factor or something like that.

[fluffy_little_something]

You used keyfollow twice in mod matrix, moreover applied it twice in each slot to the same destination. So, you quadrupled keyfollow on osc 1 volume...

Exactly. 4x. You can also do it 2x for instance, then the mute key is further down the keyboard.
My expectation is that the only thing that means is that the volume ratio between lowest and highest key increases much steeper, albeit probably not 4x for technical reasons. But for some reason there is that turnaround note, which I don't understand.

[EvilDragon]

Manual mentions around which note keyfollow centers, btw (which means keyfollow is not unipolar, but bipolar)

[fluffy_little_something]

That center key is the one whose volume should not change as I turn the mod amount knob in either direction, right?

[Chris-S]

Yes, most u-he synth are using E3 as center note. In your patch it's E4 because of transpose -12.

when the modulation value gets below zero the wave is multiplied by a negative factor

confirmed. Saw wave is flipped.

[fluffy_little_something]

I imagine it like this, just a rough drawing. But I am not sure what the line marked with a green ? represents, nor why there is that rebound. But the diagram would explain why the turn around note goes up further and further as the volume modulation increases...

[Chris-S]

The rebound is a bug in my opinion....

[Howard]

Not a bug - allowing adventurous users to flip the phase of a waveform via "negative volume" is a feature . Like most things, it's obvious once "the penny drops".

[fluffy_little_something]

What does all this have to do with waveforms and phase?
The sound seems to be the same below and above the turnaround note.

Do you have a patch that demonstrates the usefulness of that adventurous feature?

I think it makes sense to get expected, logical behavior. For instance there are certain effects which lead to a considerable volume imbalance between high and low notes. So when you try to compensate for that by modulating the volume via key tracking, there should not be mute notes on the keyboard in my view.

[Captain]

What does all this have to do with waveforms and phase?
The sound seems to be the same below and above the turnaround note.

This was already explained in this thread, but I'll have a go at it too.

It's all logical when you think about the math behind it. The KeyFollow modulation source follows the played MIDI note in a linear way. When note goes up, KeyFollow produces bigger numbers. The steepness of the line is set by the modulation depth, and assigning it multiple times makes it even steeper. No matter what, KeyFollow is always exactly 1 at the note E3. And since the modulation target is always multiplied by this value, it means that when playing E3, the modulation target (volume, pitch, whatever) is not changed at all, no matter how deep the modulation. (I think all that was already clear, but just in case. )

When the modulation is deep enough, it means that KeyFollow can go to zero and below at some point when going down the keyboard. And deeper modulation also means that the zero point goes up and comes closer to E3. If we are modulating oscillator volume (basically multiplying each output sample by the modulation source), going below zero effectively flips the phase of the oscillator waveform. This is the "turnaround note", and in most cases there is no audible difference, but the waveform is indeed inverted on both sides of the "silent note". When we continue going down the keyboard, volume starts coming back up (with inverted phase), since KeyFollow now produces lower and lower negative values.

If you want to avoid the silent note, just turn down the modulation depth so that the zero point is outside the playable MIDI note range.

Does it make sense now?

[Captain]

Double post... my first in the 16 years I have been using KVR!

[Chris-S]

If you want to avoid the silent note, just turn down the modulation depth so that the zero point is outside the playable MIDI note range.

Or, use a synth with flexible (free-mapping-curve) volume/key-scaling.

I think Zebra and Bazille can do this.

[fluffy_little_something]

Yes, thanks for the explanation.

But the question remains, what is the point of it? Why not simply leave the sound inaudible from a certain note up (or down, depending on the modulation), and freeze the increase at a reasonable max level on the other end of the keyboard?

Old hardware synths did not even have modulation matrices as such, so it is probably not an emulation of hardware behavior.

What does all this have to do with waveforms and phase?
The sound seems to be the same below and above the turnaround note.

This was already explained in this thread, but I'll have a go at it too.

It's all logical when you think about the math behind it. The KeyFollow modulation source follows the played MIDI note in a linear way. When note goes up, KeyFollow produces bigger numbers. The steepness of the line is set by the modulation depth, and assigning it multiple times makes it even steeper. No matter what, KeyFollow is always exactly 1 at the note E3. And since the modulation target is always multiplied by this value, it means that when playing E3, the modulation target (volume, pitch, whatever) is not changed at all, no matter how deep the modulation. (I think all that was already clear, but just in case. )

When the modulation is deep enough, it means that KeyFollow can go to zero and below at some point when going down the keyboard. And deeper modulation also means that the zero point goes up and comes closer to E3. If we are modulating oscillator volume (basically multiplying each output sample by the modulation source), going below zero effectively flips the phase of the oscillator waveform. This is the "turnaround note", and in most cases there is no audible difference, but the waveform is indeed inverted on both sides of the "silent note". When we continue going down the keyboard, volume starts coming back up (with inverted phase), since KeyFollow now produces lower and lower negative values.

If you want to avoid the silent note, just turn down the modulation depth so that the zero point is outside the playable MIDI note range.

Does it make sense now?