Modulation Matrix iteration and ordering

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Modulation Matrix iteration and ordering

Postby 2ManyKeys » Wed Feb 14, 2018 5:24 pm

Page 242 of the reference manual shows how the parameters of a mod matrix channel that can be modulated from another channel. This could result in some seriously complex, living sounds. It also means there has to be some evaluation order for how channel results get calculated and applied possibly to other channels.

If correct this is a really an amazing modulation system. The Fusion actually has to iterate through the modulation matrix in order to calculate the output of a channel that is then supposed to effect another channel prior to that channel's result being applied to its destination. This means the modulation matrix channel reordering shown on page 237 may be more than cosmetic. I've never seen modulation channel reordering on any other synth. Allowing reordering for cosmetic reasons only is something that doesn't usually get included because synth designers have plenty of other stuff to do that actually affects the sound. However, if the Fusion is using the channel visual order as a channel evaluation order, it may have an effect on how the mod matrix actually modulates thing. The Ion can't do anything like that!

Has anybody messed with mod matrix ordering? It should be easy to test if the order actually has audible effects.

Chan 1: Src: LFO 1, Dest. Channel 2 Amount 100%
Chan 2: Src: LFO 2, Dest. OSC1 Frequency

If the user ordering has an effect on evaluation ordering then swapping the ordering of the above two would have an obvious effect on the sound. I suppose when a voice is edited, the Fusion could always reorder the channels internally to make a channel effects everything it is supposed to.

Add to this, the fact that you have matrix 32 channels, any of which can be up to a 200 Hz multi-source S&H generator the possibilities are mind boggling.
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Re: Modulation Matrix iteration and ordering

Postby Jesse » Wed Feb 14, 2018 6:37 pm

:)

carbon111's review of the Fusion on his website was early on when people were just starting to realize a little of what was under the hood of this Beast

http://carbon111.com/fusion.html
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Re: Modulation Matrix iteration and ordering

Postby EXer » Thu Feb 15, 2018 5:05 am

I haven't tested, but I believe the user order should have NO effect on the result.

In fact, from an IT point of view, modulating a modulator is basically a product(*), and a product is commutative i.e. the order doesn't matter.

(*) if Mod m modulates Mod m', then the amount of modulation applied to the final destination is m.m' ; when the mod is 'additive' it remains a product, in this case the factor is (1+m) instead of m.

My understanding is that the user can chose the *display* order in order to see what modulates what more easily.
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Re: Modulation Matrix iteration and ordering

Postby 2ManyKeys » Fri Feb 16, 2018 10:05 am

I think you are correct. Obviously the commutative property applies. Boiling it down to simple time steps is the best way to look at it. I was overthinking it in an analog circuit fashion. Thinking in discrete time steps makes the whole thing much simpler.

For any channel, the equation is actually a couple a functions of time - not including any channel using the "table" linear transform which is just another multiplier on the source so we'll leave that out for now.
t1 = current value of time
t2 = new time value after fixed increment
source(t1) * dest(t1) => dest(t2)

So to the calculate the whole matrix, do this for every channel. Even if a modulator is modulating another modulator, the new modulator value will be available for the next run through the matrix as the t1 value.
I think this takes care of any order dependencies and even handles feedback loops like LFO1 modulating LFO2 which modulates LFO1. Maybe I should write a simple modulation matrix and test this. :-)

Good mental exercise!
Last edited by 2ManyKeys on Fri Feb 16, 2018 1:21 pm, edited 1 time in total.
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Re: Modulation Matrix iteration and ordering

Postby Jesse » Fri Feb 16, 2018 10:26 am

Sounds good be sure to post the results, preferably in a downloadable PDF file :)
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Re: Modulation Matrix iteration and ordering

Postby 2ManyKeys » Fri Feb 16, 2018 10:32 am

Don't hold your breath. I have too many projects already like looking for a pristine Fusion to show up Craigslist. :-)
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Re: Modulation Matrix iteration and ordering

Postby Jesse » Fri Feb 16, 2018 10:51 am

I think I saw some on ebay the other day
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Re: Modulation Matrix iteration and ordering

Postby 2ManyKeys » Fri Feb 16, 2018 11:27 am

Yeah, I've seen some on eBay and Reverb. Looking for the right combination of price, shipping and cosmetic condition.
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Re: Modulation Matrix iteration and ordering

Postby mstsfreak » Tue Mar 20, 2018 6:01 am

As i seem to remember, there were some problems with standard pianosounds in the Fusion. These sounds showed pops and clicks during the sustain and release phase of the envelope. We discovered that this was a problem with the volume envelope setting in the mod matrix. Moving this mod above on the mod-matrix list removed the problem. I think there is some difference in the sound when you rearrange the mods in the matrix.

viewtopic.php?f=2&t=1203&hilit=pops
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