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 Forum index » Clavia Nord Modular » G2 FAQ
Mixed mono and polyphonic aftertouch problems
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zenpho



Joined: Apr 01, 2008
Posts: 12
Location: uk
G2 patch files: 2

PostPosted: Tue Apr 01, 2008 7:41 am    Post subject: Mixed mono and polyphonic aftertouch problems
Subject description: apologies if not the correct forum area
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I started thinking about polyphonic key pressure recently, and how it is a wonderfully expressive thing to be able to hold a chord in the left hand, and play vibrato notes in the right hand.

I don't have a MIDI controller keyboard with poly pressure; but an idea hit me that I could, with a bit of tinkering, create a patch whereby the user has control over which voice the aftertouch affects. The aftertouch will still be monophonic, but the patch may be polyphonic.

The default behaviour of atertouch set up to modulate pitch is that playing a chord in the left hand whilst simultaneously adding expression with aftertouch to additional notes causes ALL notes (including the notes of the chord) to move in parallel.

The simplest way to avoid this is to create a "keyboard split"; the lower area with a polyphonic chord patch (which does not use aftertouch to modulate pitch), and a monophonic patch _with_ aftertouch pitch in the upper area.

Another, more sophisticated way (and the way I'm having problems with) is to dynamically route aftertouch messages to the most recent voice in a polyphonic patch.

Posted Image, might have been reduced in size. Click Image to view fullscreen.
I use OS v1.40 with an unexpanded G2 Engine.

The blue MUX unit near the top is supposed to make sure that the aftertouch message is routed only to the most recently activated voice.

Unfortunately the result is that all three oscillators receive the aftertouch messages. Try playing the patch and you'll see that using aftertouch results in all oscillators moving pitch in parallel.

The cause of this problem (I think) is that I'm trying to mix monophonic and polyphonic behaviour in the same patch: There are actually three DSP instances of the MUX, operating in parallel.

When one voice is on - only one aftertouch message is routed to one oscillator. When a second voice switches on the first MUX+oscillator pair are still connected, so aftertouch messages move both oscillators in parallel.

----
I tried moving the MUX to the monophonic FX area...

Posted Image, might have been reduced in size. Click Image to view fullscreen.

...but the multiple instances of the Status module providing the Voice Number value mix together and the monophonic area is permanently receiving a value of 12 (values 0, 4, and 8 in the separate polyphonic instances are adding up to make 12).

I'm wondering if any guys who experiment with the G2 in unusual ways can think of a workaround for this problem?


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Blue Hell
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Joined: Apr 03, 2004
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Location: The Netherlands, Enschede
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PostPosted: Tue Apr 01, 2008 8:31 am    Post subject: Reply with quote  Mark this post and the followings unread

When in your first patch you would leave out v2 and v3 you would only have the after touch on the FM input of one voice.

The way you routed it after touch for voice one goes to V1, for voice two to V2 etc. You do not need to throw three oscillators in as the voice mechanism already makes three out of each one you placed.

Still, in the one oscillator setup, the after touch would not affect the last voice played but an arbitrary one, as the key allocation is sort of arbitrary over the voices (depending on the playing history).

Maybe there would be a trick using the monophonic kbd input and a s&h to get the voice nr of last voice played ... hard to check here at work though ... and even at home as I don't have a keyboard Very Happy

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Blue Hell
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Location: The Netherlands, Enschede
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G2 patch files: 318

PostPosted: Tue Apr 01, 2008 1:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

Something along these lines maybe ... I used CC2 to emulate after touch here. The idea being that the simulated after touch is only passed for the voice in which the last note is the current note.

The patch differs a bit from the picture to illustrate the workings better, but it's the same idea.


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zenpho



Joined: Apr 01, 2008
Posts: 12
Location: uk
G2 patch files: 2

PostPosted: Tue Apr 01, 2008 2:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Wow... You patched all this without a keyboard! Thanks very much indeedie. ;o)

I just looked at the jpeg and it looks like it could work (i'll try the patch in a minute) I'm impressed at the speedy response, and very grateful!
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Blue Hell
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PostPosted: Tue Apr 01, 2008 2:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, well, I do have an engine of course Wink

I'm not sure if it's OK and what you meant ... we'll see about that Laughing

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zenpho



Joined: Apr 01, 2008
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Location: uk
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PostPosted: Wed Apr 02, 2008 2:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, I tried the patch this morning with your simulated keyboard triggers in the FX area, and also with my controller keyboard.

It seems to work for two voices simultaneously, routing pitch modulation messages to the most recently triggered voice - but the engine is still behaving strangely when it comes to more than two voices.

I've cooked up a patch (with simulated keyboard in the FX area) to demonstrate the strange behaviour.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

The patch should behave as follows:
1. Move to the FX area.
2. Trigger the [LowPair] button - to start a pair of low notes.
3. Trigger the [High] button - to start a final high note.
4. Lastly, trigger the [Wobble!] button - pitch modulation information should only the high note.

Unfortunately, on some occasions - the high note won't be affected, you can hear the low notes clearly wobbling whilst the high one stays unaffected.

Another test:
1. Set all the buttons so that all notes are off and no wobbling occurs.
2. Trigger the [High] button first this time - starting a single high note.
3. Trigger the [LowPair] button - starting a pair of low notes.
4. Lastly, trigger the [Wobble!] button - only the G in the low note pair should be wobbling.

Sometimes the high note is affected, even tho it was clearly not the most recent note.

---
I think this strange behaviour is probablyall down to the unpredictable (or atleast very complex) polyphonic voice allocation again, and the fact that there are 3 polyphonic instances of the inverting mixer (used to flag identical note values?) is connected to 3 instances of a MonoKey module.

I have a feeling that the MonoKey module isn't consistently reporting the same value across all 3 polyphonic voices and that the 3 inverting mixer instances occasionally incorrectly report an identical note.

I wish there was a way to have more control to the user over the internal voice allocation and polyphonic behaviour.

----
Maybe it would work if the patch was "monophonic" to turn off all the internal voice allocation, but had a bank of parallel oscillators and a mixer. It could count note on/off messages, and trigger individual envelopes and pass aftertouch messages to only the most recent oscillator.

....that sounds like a lot of work tho! ;o)

I'll keep at it, and I'll you posted if I make any breakthroughs - thanks for your help so far!


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Blue Hell
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PostPosted: Wed Apr 02, 2008 2:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

It's not working OK indeed, I tried some more stuff, to no avail .. I'm out of ideas. It would be helpful when the mono key gate would only go active for the voice the last note played happens to be in ...
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