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AlenK

Duophonic Emulation

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Greetings XW enthusiasts,


I’m posting this in the XW-P1 part of the forum even though I believe it will apply equally well to XW-G1 because I think more people will read it here given the far greater number of P1s out there.

 

If you happen to be fortunate enough to own one of Korg’s recreations of the famous ARP Odyssey, or own an original ARP version, you are well aware that it is actually a “duophonic” synthesizer. That is, it is capable of playing two pitches at one time. When two keys on its keyboard are pressed, one of the Odyssey’s two oscillators plays the pitch corresponding to one key while the other oscillator plays the pitch for the other key. “Duophonic” is in quotes because the Odyssey isn’t actually playing two individually articulated notes;  both oscillators pass through the same filter and amplifier.

 

I have recently discovered for myself a way to emulate this behavior in the XW’s solo synth. I say “for myself” because I may not be the first to have discovered it. And it may well have been described here already. However, I am aware of only one other post on the matter of duophonic operation.

 

Here’s the method:

 

Program oscillator Syn1 with a KeyFollow value of zero (00) rather than the normal +64 and a KeyFolBase value of C- instead of the standard C4. Program a virtual controller with NoteOnKeyNum as the source, a depth of 127 and KeyFolBase of Syn1 as the destination. Choose whatever wave and envelopes for Syn1 you desire. If you want a simple duophonic sound, program Syn2 with the same wave and envelopes but leave its KeyFollow and KeyFolBase parameters at their default settings. Of course, you needn't use the same wave or envelopes.

 

When you play a key the pitch of Syn1 will correspond to NoteOnKeyNum, which is simply the MIDI note number. The pitch of Syn2 will be identical. When you now play a second note without releasing the first note the pitch of Syn1 will continue to correspond to NoteOnKeyNum. The pitch of Syn2, however, will correspond to the actual pitch of the second key you pressed.

 

This works because, in the case of the synth oscillators (Syn1 and Syn2) the NoteOnKeyNum value they receive appears to always be that of the first key pressed. Hence, pressing a second key does not change the value that Syn1 receives through the virtual controller whereas Syn2 responds normally. (PS. The PCM oscillators don't respond to NoteOnKeyNum in the same way, as it turns out. I initially had hopes of assigning two oscillators to each of the pitches but so far I haven't found a way to do it.)

 

The legato parameters of each of the two oscillators greatly affect how their individual envelopes respond to key presses in this “mode” of operation. There are four possible combinations and each yields a different result; which of them is “right” for a given piece of music will depend on the music.

 

This technique has one major limitation. Since the pitch of oscillator Syn1 depends entirely on the NoteOnKeyNum value passed through a virtual controller, portamento is not supported for it. Turning it on has no effect whatsoever. You can, however, freely apply portamento to oscillator Syn2, which is an interesting effect in its own right.

 

 I have uploaded an example. Yes, it really does work.

 

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I haven't been here in ages but happened to log on to look for MZ-X 500 info and saw this thread.  Years ago I tried something like this, though your method is much better.  I just used the footswitch to disable the key follow of an oscillator.  Assuming the key follow is at the default setting (+064), you can just use a virtual controller with Hold 1 as the source with an amount of -127, and assign it to key follow.  Of course, it doesn't have to be the footswitch assigned as the source, other things work as well.

 

It still won't work with PCM layers (it will just revert to the key follow base note), but you can use portamento.  The big problem is you have to press the footswitch at the right time, or else the pitch will go to whatever the key follow base is set at.  I like your approach far better as you can play much faster because you don't have to worry about hitting the pedal just right.  Also, you can directly play two notes at the same time and it works. 

 

I just tested now and you can kind of get the PCM layers to work if you combine methods.  Use your way except have key follow at +064, and then use the hold pedal to set key follow to 0 when activated.  I am tired right now so perhaps I am just imagining that this works.  :)

 

I always wished you could just assign different note priorities to the layers in the solo synth to achieve duophonic playing.  A paraphonic mode would've been great, too.

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If you use Soft instead of Hold1 the notes won't sustain when you use the pedal. Of course maybe you _want_ the notes to sustain as well. You can compensate for the small drop in volume caused by Soft (if it matters.. it's not much of a volume change) using another virtual controller. 

 

Ain't them virtual controllers wonderful?

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Works just as you describe on my G1, Alen. What a neat trick! Very useful.

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My XW's are still en-route to my home in the USA (according to the shipping tracker, they are soon to be docking in the NE USA, then hopefully they'll finally be transported to me around the end of April). I am very curious to hear this duophonic emulation. Can anyone upload an audio file with it in action to satisfy my curiosity until I get to try it for real?

 

 

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Chas, did you get your XW back?

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On 5/31/2017 at 2:54 PM, AlenK said:

Chas, did you get your XW back?

 

Alen, yup, and you've already commented on my "shippers" thread!

 

I'm still in the process of unpacking and sorting my gear, and yes, now I have my XW's I can finally try this duophonic style feature for real. But, part of me just wants to fiddle away to my hearts content with my gear such as my XW's, then the other part says, "look at all that packaging junk all over the place, and the room is a MESS. Get tidying!" So I am trying to discipline myself to get everything unpacked, tested, and put away/ in place in an orderly manner first before jumping in to experimentation and noodling. I must add though, that your patch is already downloaded onto my computer and awaiting transfer to my XW's!

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