Another "does this effect exist" thread - resonant sympathetic filter bank

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I was experimenting with my nord micromodular with an effect I thought of, in thinking about "sympathetic" effects, similar to sympathetic strings.

In concept it is simple, though in execution (physically building) it might be pretty complicated.

Here is the idea - around 8 to 12 resonant filters in parallel, set close to self oscillation, tuned to either chromatic or other scales or modes (each filter tuned to a note in the scale). When you play, different notes you play "ring" the filters and make it play sympathetically along with what you play. You tune it to the scale you are playing in.

On mine (in the nord micromodular), I put a waveshaper after each filter to get more harmonically rich sounds than the sine-like wave that naturally comes out of a resonant filter.

A mixer at the end to mix the filters back together.

Does such an effect exist in analog? Not worth it?

[R.G.]

Don't know of one, but it's one of those dead simple concepts to do. Execution might get tricky.

Look up a state variable filter. There's one inside the Mutron and the Neutron clone of it. Make a dozen; needs 4 opamps, so two duals  or one quad per filter.

Set it up to be on the frequencies you want, per filter. Then up the "Q" to resonance and back it down a bit. All done.

[cloudscapes]

I know what you're talking about, I've also got a nord modular
love the effect!

sure its possible, but massivly paralelle. easiest way I ca n think of is having several ssm2044 filter-on-a-chip. very knobby project though

[space_ryerson]

For some reason this idea reminds me of vocoding, probably because of the parallel filter bands. I can't think of how you could trigger the self oscillation like that with one, though.

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if anyone wants to hear what this sounds like (done digitally with the nord modular) go here:

http://www.soundclick.com/bands/default.cfm?bandID=1016735&content=music

several takes with different combinations of settings

it is strange how much it sounds like a digital pitch shifter at times

[Rectangular]

this reminds me a bit of the EMS 8 octave filter bank. I still need to clone one of those.  8 filters in parallel, separated over 8 octaves

I've got a "formant filterbank" that can do something like this, but its only got 3 filters, rather than the desirable 8-16

[earthtonesaudio]

I can see it now... 

Analog emulation of Autotune/Pitch Correction, coming to a DIYstompboxes near you in early 2010!!!

[Processaurus]

I like your science experiments!  I think you'd actually need twelve chromatically tuned filters, and have analog switches control their on/off state, so that there are only 8 on at a time.  Like the felt mutes on an auto harp.  With a jillion diodes you could use a 12 position switch to send out the combinations of channels to mute (half as much work as telling which channels to be on,  there's only 4 per key you'd generally not want on). 

Or just have toggle switches for each channel and know your scales...

I don't think it would be that much work, if you made a pcb with a bunch of identical channels.

[Strategy]

I use Audiomulch software and it has an object (5combs) in which 5 parallel short delays are tuneable to notes on the scale. Your input sound provides an impulse to the delays, essentially the delays are used additively. It gives a similar effect to what you are describing.

A flanger by Juergen Haible, the Son of Storm Tide (www.jhaible.de) features a 1V/octave input for being able to 'play' flanger feedback oscillations. You could get sympathetic tones this way.

For filters responding in a sympathetic way, it's true Vocoding would be ideal.

Haible has just issued a neat resonator that is the Polymoog resonator. Would make an ideal large-ish pedal project if you don't mind doing your own power supply with his onboard section and a little transformer. This is a 3-band resonator switchable between high, low, band and band-notch. With the resonance up and careful tuning you are likely to get a lot of the 'harmonized' sympathetic resonances you're talking about, esp mixing dry signal in. I plan to do this project!

- Strategy

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I like your science experiments!  I think you'd actually need twelve chromatically tuned filters, and have analog switches control their on/off state, so that there are only 8 on at a time.  Like the felt mutes on an auto harp.  With a jillion diodes you could use a 12 position switch to send out the combinations of channels to mute (half as much work as telling which channels to be on,  there's only 4 per key you'd generally not want on). 

Or just have toggle switches for each channel and know your scales...

I don't think it would be that much work, if you made a pcb with a bunch of identical channels.

In the sound examples, there are 12 filters, but the filters are tuned to the C major scale, with an extra flatted 7th - it ranges over about an octave and a half I think. The filters on the nord are modeled after analog filters, so I don't think the sound would be too much different with analog filters from what you hear there. You could get a pretty close sound to this with just 8 filters I think... even six maybe, if you tuned them over a wide range, as a lot of times the filters ring from harmonically related notes as well as the fundamental they are tuned to.

The octave up effect in the sound sample is from each filter fed to the two inputs on it's own ring modulator (12 ring modulators total) - this would make for a pretty large effect if you were to build it physically (two transformers for each filter), but it is a pretty cool addition.

[alex frias]

I used to use an effect called "DRONE" from a KORG ToneWorks cheap AX1g and liked a lot to add some resonating drone to a especified note. It just shows itself when you pass by the especified pitch note or a perfect fifth of it, in any octave. Sadly I gave or exchange the unit, don't remember... I would love to experiment it with my Dano modified with a GOTOH Buzz Bridge...

But you may get some idea of how it sounds by watching this vid:

http://www.youtube.com/watch?v=raxvU9-yxL4

The level of the effect is more to the subtle side of things, but can be heard. I would love if the guy had a well tuned guitar, but the performance is quite good, with interesting articulations and exoctic bends.

I think if the implementation on digital domain of this kind of effect could be easier to obtain than on the analog world...

[GFR]

Not a stompbox, but:

http://soundbytes.de/Sympathizer/

[Top Top]

I used to use an effect called "DRONE" from a KORG ToneWorks cheap AX1g and liked a lot to add some resonating drone to a especified note. It just shows itself when you pass by the especified pitch note or a perfect fifth of it, in any octave. Sadly I gave or exchange the unit, don't remember... I would love to experiment it with my Dano modified with a GOTOH Buzz Bridge...

But you may get some idea of how it sounds by watching this vid:

http://www.youtube.com/watch?v=raxvU9-yxL4

The level of the effect is more to the subtle side of things, but can be heard. I would love if the guy had a well tuned guitar, but the performance is quite good, with interesting articulations and exoctic bends.

I think if the implementation on digital domain of this kind of effect could be easier to obtain than on the analog world...

That is pretty cool... I am guessing that it is actually a similar concept in it's programming, though the sympathetic ringing has been shaped more to make it more "buzzy." It is digital, but I would bet it is based on the basic idea of a filter tuned to certain pitches. I actually like that sound better... may try to refine a little bit to see if I can get that more buzzy sound, which is what I was really going for in the first place.

I am not sure if I would actually ever physically build this... some things are just so simple to throw together in the nord that I can't justify the weeks or months I would spend designing and building it...

If I could pare it down to just a couple of filters (2-3) and some shaping to get that buzzy sound, I might though.

[alex frias]

I agree with you that the principle is similar.

I even think about to have two or more of this tuned drones...

[CynicalMan]

I'd be interested in a version of this with 2 or 3 adjustable filters. 12 would be great but it would be very big in terms of controls. A 2 or 3 filter version with extras such as length of oscillation, oscillation tone, individual on/off switches (maybe use the pots with switches at the beginning of the rotation) might be more useful. Still, wait two years and EHX will probably come out with a 12-filter version using sliders.

[alex frias]

Maybe six monthes...