Rossum Electro-Music Morpheus Filter

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Marco Alpert
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Post by Marco Alpert » Sat Mar 24, 2018 2:46 pm

JC14 wrote:Agreed. Hope there is a workaround or anything like that... This makes the sequencer pretty much unusable (for me). Unfortunately.
Hi all,

For the reasons mentioned above, I'm afraid there aren't really any workarounds that give true arbitrary-duration filter morphing without passing through the Null Filter (apart from buying a second Morpheus and crossfading between them with VCAs - not that we necessarily recommend that as a solution, but hey...).

However, using the Fade Time commands in the Filter Sequencer, you can shorten the transition times such you don't really hear the raw sound for any substantial period of time.
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Post by akrylik » Sun Mar 25, 2018 6:45 am

Idea #1: Instead of the Null Filter, fade to a computationally cheap one-pole LPF with cutoff set in between the start and end filters.

Idea #2: Make sure the total loudness (energy) of the Null Filter matches the total energy of the starting filter while fading.

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Post by fylthymcnasty » Sun Mar 25, 2018 7:03 pm

akrylik wrote:Idea #1: Instead of the Null Filter, fade to a computationally cheap one-pole LPF with cutoff set in between the start and end filters.

Idea #2: Make sure the total loudness (energy) of the Null Filter matches the total energy of the starting filter while fading.
Marco, these are the kind of workarounds I was hoping could be implemented - not user workarounds for the filter sequencing as it operates now, but tweaks to the OS which will make this a usable feature. I do understand that true filter morphing can't be acheived, we get that, but there must be other ways you can rework this feature in the firmware so it works better - hence my hope that you guys could brainstorm this and implement another way. I know that Dave is about as clever as a person can get, I'm sure there is something he can come up with that works better than it does now. Incidentally, what was your expected real-world use of this filter-sequencing feature, as it performs currently?

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Post by Mostin77 » Mon Mar 26, 2018 4:41 am

I absolutely love the z-plane filters in my emu ESI4000 and was thinking of upgrading to a E4XT Ultra...now I’m thinking Morpheus might be a better plan.
What a module! :eek:

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Post by Marco Alpert » Tue Mar 27, 2018 2:44 pm

Hi all,

I passed the various comments about filter transition on to Dave and here's what he says:
Marco has asked me to contribute my thoughts on this thread. First, I’d like to clarify the problem. The original E-mu Morpheus (which we all know had only one dimension of real-time morphing, no control over distortion, and filters that could sometimes go unstable) didn’t suffer from this concern because it was a polyphonic module: Just like Marco’s tongue in cheek suggestion of using two Morpheus modules, the E-mu Morpheus never switched cubes during a note, it just began a new note.

So this was one of the many new issues we had to confront when updating the Morpheus technology to modular synthesis: what do do with the audio when changing the cube?

As suggested above, one “ideal” solution would be to run two cubes in parallel, and crossfade between them. This obviously requires that the module be able to run two complete morphing cubes in real-time, thus twice the processing power is needed to handle this one issue. To step up the processing power enough would require moving to a much more expensive class of CPU; we might have instead removed a morphing dimension and some other features; both seemed like poor trade-offs.

One might think morphing between the outgoing and incoming cubes would be the “ideal” transition. But the real world bites you in the ass. Such a transition not only requires another doubling of the interpolation math, it would also require some very sophisticated algorithm to deal with potentially colliding "modes."

As Marco has explained, the cube design has many constraints. One way to understand this is to think of the 14th order filter as including up to 7 resonant “modes,” each of which can store audio energy. As the filter morphs within the cube, the modes morph in frequency and resonance, and the frequency and phase of the audio energy stored therein moves around with the modes. One cardinal rule is that two substantially resonant modes never cross, and thus never briefly occupy the same frequency, otherwise they transfer energy between them based on relative phase, often with explosive results. Furthermore, it’s not clear if the outgoing cube has modes full of energy, that that energy should be transferred to the "corresponding" modes of the incoming cube. After all, the cube library was carefully designed with respect to mode trajectories, but there is no designed-in "correspondence" of modes between different library cubes, so energy in a high-frequency mode of the outgoing cube could end up in a low frequency mode of the incoming cube. The bottom line is that morphing between cubes at transition time is far from practical for many reasons.

The sensible alternative, it seemed to us, would be to quell the energy in the modes of the outgoing cube, and let the incoming cube acquire its own energy. There were two approaches: to morph from the outgoing cube to null, then back to the incoming cube; or to crossfade rather than morph. I tried the morphing approach first, but here again the trajectories of the modes from an arbitrary point in library cubes to the null filter was not designed in, and as a result many of the transitions were ill behaved and sounded horrible. I tried a number of hacks, but ultimately surrendered to the crossfade approach.

Again, as Marco has pointed out, a quick transition (we support transition times as short as 10 msec - that’s less than 5 cycles at 440 Hz) does a pretty good, but not ideal, job of minimizing transition null filter “bleed-through” artifacts. If there’s a simple fix, it would be to extend the low end of the transition time variable to as little as 1 msec or even less. That's certainly worth a try if it addresses the problem.

The suggestion of fading to a modest lowpass filter instead of a null filter, while more complex that the above, is practical and would seem to have merit in lowpass cases, but I'm concerned it exacerbates this issue for other common cases, such as highpass, allpass, or formant. Indeed, maybe fading to silence rather than null might be a more general solution. It’s not clear to me any of these is per se better than a null filter in the general case, but it could be there’s a way that a few choices could suffice. That's a fair amount of work, but not impractical. It might be that allowing a programmable gain for the null filter specified as part of the outgoing filter's transition parameters would be as good as anything, and that seems quite practical.

Brainstorming is fun, though! The suggestion of estimating the loudness or energy (they are a far cry from the same thing) and trying to equal that in the gain of the null transition would be a research project of major magnitude in itself, given that the energy is often stored in the complex variables of the modes, and we are trying not only to match the outgoing but also the incoming cube. Any takers?

Since the contributors to this thread have been so kind as to toss me a challenge to think about, let me turn the tables. I’ve said in several interviews over my career that one of the things that impresses me most about the talents of the musicians who use my instruments it their ability to take something I viewed as a flaw in my design, and instead turn it into a key musical element in their compositions. So my challenge to you is this: find a way to turn the existing Morpheus transition behavior into an expressive component of your music!
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Post by duck1887 » Tue Mar 27, 2018 3:23 pm

Marco Alpert wrote:Hi all,

I passed the various comments about filter transition on to Dave [...]
Before I even read this I just need to say: We love you Dave! :hug:

Sorry, back to the thread now :oops: :tu:

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Post by JC14 » Wed Apr 04, 2018 10:53 am

I hear mixed stories about the Morpheus. Nice options and possibilities, but also complaints about very annoying differences in loudness when switching between / auditioning filters.
Is there a solution for this? Can't you edit and save presets of each filter, adjusting the volume output or something like that..?

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Post by bemushroomed » Wed Apr 04, 2018 10:59 am

JC14 wrote:I hear mixed stories about the Morpheus. Nice options and possibilities, but also complaints about very annoying differences in loudness when switching between / auditioning filters.
Is there a solution for this? Can't you edit and save presets of each filter, adjusting the volume output or something like that..?
Yeah, i re-saved a lot of filters where the volume was like 2-4x higher. Now they have an even volume and it's possible to browse the filters without waking up the whole neighborhood + ruining your hearing for life :P

I like the filter(s) a lot. What i don't like is the distortion which i've just turned off on probably 99% of the filters that uses it.. i love distortion but not the digital kind.
Last edited by bemushroomed on Wed Apr 04, 2018 11:07 am, edited 1 time in total.

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Post by damase » Wed Apr 04, 2018 11:07 am

Much appreciate Dave addressing the concerns here

Honestly the programable gain of the null filter if it could be saved per sequence that would seem like a pretty reasonable solution to me. Not ideal, sure, but better than the current scenario. But the thing that might complicate this is if you want to use the null filter as one of the filters in the sequence... for example i like to have null filter available as a fast way to bypass the filters altogether... this would turn it into an attenuated bypass and really complicate the gain structure. I think having an option to fade to silence inbetween would be nice... even if still not ideal having the option would be cool.... then you could also kind of use the sequence fade time as a unconventional open/close stereo VCA which could yield more sonic possibilities.

Is there ever plans for additions of more cube models? If so, id like to get some thoughts in about those ideas as well. Admitedly i havent tried to customize and save my own but from what I can tell its more of modifying currently existing cubes rather than creating new ones

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Post by NathansModular » Wed Apr 04, 2018 11:36 am

First I just want to say I got into eurorack strictly becuase of the rossum morpheus. I absolutely adore it and recommend it to everyone.

damase wrote: Is there ever plans for additions of more cube models? If so, id like to get some thoughts in about those ideas as well. Admitedly i havent tried to customize and save my own but from what I can tell its more of modifying currently existing cubes rather than creating new ones
I want to hear those ideas! I personally would like some cubes with a little more freedom instead of being limited to the designers sweet spot. I think a three sisters cube would be nice.

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Post by Trooper » Thu Apr 05, 2018 1:27 am

:tu: Me too, the morpheus with it's legendary Z-plane filters throw me into modular, and it (and the Evolution) are still my best filters. I can also recommend them both.

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Post by NathansModular » Thu Apr 05, 2018 1:57 am

Trooper wrote::tu: Me too, the morpheus with it's legendary Z-plane filters throw me into modular, and it (and the Evolution) are still my best filters. I can also recommend them both.
Thats so cool! It is very difficult to make tbe sound from a morpheus on anything else. Parallel filters nope. Series filters nope. So nothing in euroland (or elsewhere really) can replace it. I am personally lusting hard for a control forge now (got morpheus and soon a assimil8or) with two satellites. I think that the Morpheus evolution filter was a smart idea as they clearly are the perfect compliment.

What blows me away is how good the rossum sounds in resonant cubes feeding clicks in.

My real dream now is 2 or 3 channel rossum effects unit for sound design. I have never bought an effects unit in 15 years of playing guitar and 6 years of playing synths. I would break that for a Rossum Nexus (my fantasy name for this device).

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Post by Trooper » Thu Apr 05, 2018 2:06 am

I very like the possibilty to build sequences, with for example 20 different filters, all called step by step from an external LFO or similar. Whole sound worlds to be discovered... :tu:

The evolution is for me the maximum for "old style" sounds, like moog and so on.

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Post by Funky40 » Thu Apr 05, 2018 8:02 pm

Is anybody here using the Morpheus to filter a Drummachine or a Elektron box ?

in regards to filter switching ( from midi2CV):
one can setup a chain of filters one wants to switch thru, any (reasonable) numbers of filters, right ?
is this working well when controlling from midi with a midi2CV device ?
guess one would just have to set the numbers of filters to 4,8,16, right ?

i just imagine a Octatrack or Digitakt been fed thru a Morpheus while the Morpheus would be controlled by the midi out of the same machine.


any feedback on this from people doing so would be much appreciated
For sale / reduced prices ( swiss (we are NON-EU)/ in case it makes sense_ EU/WW)(CHF +- = $):
lowered prices: Dotcom Q960: 650.- / Q119: 420 / ( i also have one or much likely two 19" Frames)
ATV A-Frame incl. Accu and Bag: 830.-, like new, quasi unused.

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Post by damase » Thu Apr 05, 2018 8:38 pm

Funky40 wrote:Is anybody here using the Morpheus to filter a Drummachine or a Elektron box ?

in regards to filter switching ( from midi2CV):
one can setup a chain of filters one wants to switch thru, any (reasonable) numbers of filters, right ?
is this working well when controlling from midi with a midi2CV device ?
guess one would just have to set the numbers of filters to 4,8,16, right ?

i just imagine a Octatrack or Digitakt been fed thru a Morpheus while the Morpheus would be controlled by the midi out of the same machine.


any feedback on this from people doing so would be much appreciated
Of course you can do that and its great! Just note that the sequencer advances by trigger pulses only via inc, dec, and reset jacks... and not CV.
Not sure what you mean by needing certain sequence numbers... you can add any number of filters you want to your sequence, including fade times in between and other little tricks. With drums, i find there is a lot of filter cubes that will explode your low end far too much, so you gotta be careful of your filter choices and customize the gains(saved to the cube preset that the sequence is recalling)
damase wrote:

Is there ever plans for additions of more cube models? If so, id like to get some thoughts in about those ideas as well. Admitedly i havent tried to customize and save my own but from what I can tell its more of modifying currently existing cubes rather than creating new ones


I want to hear those ideas! I personally would like some cubes with a little more freedom instead of being limited to the designers sweet spot. I think a three sisters cube would be nice.
I would LOVE for there to be more performance oriented cubes. A lot of the cubes are super cool for experimental sound design, which i do really love all of them. But i would love to see some others that have more tame purposes for the knob, and more relaxed on the gain boosting by the modulation so that they are dependable and useful in the live setting. Maybe one that is kind of like the wmd overseer, and sure other emulations would be interesting and wecome in my mind... some simple ones that have at least 1 knob acting as VCA, lowering the entire frequency range. Some kind of filter thats a passes a HP and LP filters with resonance that can be separately adjustable like a lot of synth voices have. And even one that is basically a 3 CV input stereo VCA would be super useful. Just seems like most of the current ones are super complex soundwise so a few more familiar designs would be nice i think.

On a coffee filled morning im sure my mind would come up with more...

Ive been using it live recently, and theres a few filters which have made the cut into my live sequence, but i still wish i had a bit more control over them in a way that makes sense rather than twisting knobs with a general idea of what might happen

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Post by melittophily » Fri Apr 06, 2018 9:02 am

High Wolf wrote:I'm experiencing a bit of noise / hiss when using the frequency knob, but seems not with all cubes...anyone else has the same issue?
Going back a few pages to October - I do get crackly noise sometimes when adjusting the frequency knob or its mod amount attenuverter, but not from CV. Its something I’ve been meaning to email Rossum Electro about but just haven’t gotten to it.

I eagerly awaited this filter through its development - I really wanted an Emu Morpheus as a teenager but couldn’t budget it. So I saved and got it shortly after release, and I’m still very happy with it besides the frequency knobs issue above. Honestly, I could have done without the sequencer entirely, so for me its just a way to organize cubes and cut down on select knob scrolling time. I’m not as excited about vanilla filters as most and I am happy currently using only it and Laurentide passive LPGs for subtracting in the modular. Dave’s SSM2044 in my Kawai K3 is probably my favorite regular VCF so I’m thinking I want the Doepfer SSM and a pair of utility state-variable ones like Bastl Cinnamon or 2HP and that can be all for me. I use two Bastl ABC mixers for pre- and post- stereo imaging and gain staging and it works great.

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Post by Funky40 » Fri Apr 06, 2018 5:20 pm

damase wrote: Of course you can do that and its great! Just note that the sequencer advances by trigger pulses only via inc, dec, and reset jacks... and not CV.
Not sure what you mean by needing certain sequence numbers... you can add any number of filters you want to your sequence,
Thank You damase
For sale / reduced prices ( swiss (we are NON-EU)/ in case it makes sense_ EU/WW)(CHF +- = $):
lowered prices: Dotcom Q960: 650.- / Q119: 420 / ( i also have one or much likely two 19" Frames)
ATV A-Frame incl. Accu and Bag: 830.-, like new, quasi unused.

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Post by geremyf » Wed May 09, 2018 3:01 pm

So regarding the filter sequencing, and having to go through null before the next filter in the sequence: I understand that there is nothing to do with drones, but with any note sequence, isn't the idea to step the filter sequence when you have the gate off on the VCA, so you don't hear the null filter output? I would think just inverting the gate that you use for the VCA on the step input would do the trick? I am considering purchasing a morpheus so I'm curious.

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Post by Migrigsynth » Thu May 10, 2018 11:07 am

melittophily wrote:
High Wolf wrote:I'm experiencing a bit of noise / hiss when using the frequency knob, but seems not with all cubes...anyone else has the same issue?
Going back a few pages to October - I do get crackly noise sometimes when adjusting the frequency knob or its mod amount attenuverter, but not from CV. Its something I’ve been meaning to email Rossum Electro about but just haven’t gotten to it.

Yes, I just started noticing noise when adjusting the Frequency knob. Sounds almost like a dirty pot on a mixer.

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Post by Dogma » Mon Jul 02, 2018 6:48 am

edit
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look up!

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Post by Dogma » Tue Jul 03, 2018 7:35 am

edit
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look up!

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Post by pzoot » Tue Jul 03, 2018 2:44 pm

When was it updated?

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Post by RMNC » Tue Jul 10, 2018 12:21 pm

If it was possible to eschew stereo and run two separate mono cube instances on R and L then we could gain all the numerous advantages of a multimode filter and sidestep null by simply crossfading. Assimil8or probably receives the most development attention, but it seems like if the two Morpheus channels are discrete for stereo, the DSP could just as well be executing two different simultaneous cubes that we could then blend or pan, feedback, etc. Some internal pipes to bypass AD/DA for achieving series or parallel operation once this is in place would also be really nice.

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Post by 4eyez » Fri Aug 10, 2018 3:48 pm

Thinking about picking one of these up. Beyond the standard filter usage, how do people like for pingable resonators? I wasn't finding many examples of that usage on YT.

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Post by PLNB » Fri Aug 10, 2018 7:28 pm

I have a feeling I will buy another Morpheus once these recent requests are implemented. The CV controls plus attenuvertor on the modulation side was really nice. The sequences, ringiness, and loudness jumps between patches was a struggle to take advantage of without alot of preplanning/menu diving. Maybe a simpler OS can be made available to trim down and simplify the sequence side of the filter?

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