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Where are all the Eurorack tracking generators?
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Author Where are all the Eurorack tracking generators?
Videographics
I don't seem to be able to find ANY tracking generators for Eurorack. It's not a category on ModularGrid and extensive searches for them yield nothing. I found and old thread mentioning a Grant Richter DIY project (with a picture!) and an LZX module, but most of the links are dead and, as far as I can tell, neither is a real thing.

What's a tracking generator? A tracking generator let's you scale (or distort) output levels based on input levels at multiple points across a range. You might think of a tracking generator as a multi-band equalizer for voltage levels instead of frequencies.

The classic use of a tracking generator is to scale and shape velocity levels across the range of a keyboard to emphasize certain parts or tame hotspots — but there are tons of other applications. How about warping the shape of a triangle or sawtooth LFO? Or add some extra complexity or emphasis to some part of an envelope. You could process a stream of S&H output to 'favor' or 'minimize' various ranges of values. Process sequencer output for global control over the accented or emphasized steps. Or, 'tame' the output from experimental controllers so they play more musically and are easier to control.

There are so many great uses for them that Oberheim put five 5-point tracking generators on every voice of their classic Matrix 12 and Xpander analog synths! (That's right, every Oberheim Matrix 12 actually contains 60 independently controllable 5-point tracking generators!) And many soft-synths have very elaborate tracking generators. The Yamaha DX/TX synths also have some more limited tracking generators with level-scaling breakpoints, curves, and depth for every operator that are essential for its sound.

Tracking generators are damn useful for all kinds of synthesis applications. So where are all the Eurorack tracking generators?!
luketeaford
Isn't this something you could achieve with an addressable sequencer? 'Cause I do that but haven't heard it called a tracking generator.
mrerdat
You could probably patch one using a CV addressable sequential switch.
Though depending on how the switch is designed you might hear clicking if you're using it for audio vs CVs.
jamos
Yeah, puzzling. I loved having that in my Xpander.

Surely someone makes one under some other name?
Jumbuktu
As I understand it, you are looking for something like a 'transfer function' processor. You put in CV x and it outputs CV y, where y is some function of x.

From that point of view, attenuators, offsets and other CV uitilities qualify, although my guess is that you want non-linear functions. VCAs with exponential resonses would qualify.

A quantiser also qualifies, since it essentially processes a single input to produce a single output based on some functional rules. You could use Quantermain in Ormanent&Crime, with some custom 'scales' to creat 4 transfer functions configured for particular uses.

Modules like O&C and Disting are open-ended enough for someone to be able to write a transfer function app if there was sufficient demand.
Videographics
luketeaford wrote:
Isn't this something you could achieve with an addressable sequencer?


I don't think so, but that's an interesting idea. An addressable sequencer could provide different 'adjustment voltages' at each step, selected based on the input level, but as far as I know an addressable sequencer can't address an infinite range of steps in-between the sequencer's actual steps to generate in-between values.

To go back to the equalizer analogy... I imagine trying this with an addressable sequencer would be analogous to having a bunch of brick-wall crossover filters spread evenly throughout the frequency range, instead of having a bunch of smooth parametric EQ bands with adjustable frequency.
luketeaford
No, there would be as many steps as the sequencer has stages, but you could also use the CV you get out of that with vcas or multiplication so that an incoming voltage in a certain range would be remapped according to the new voltage in some arbitrarily complicated way. Each of the stages on some sequencers have gate outputs, so you could conceivably even switch them around.

Is a 5 step addressable sequencer used in this way equivalent to the 5 point tracking generator you mention?
brandonlogic
Mutable frames? hmmm.....
Videographics
Jumbuktu wrote:
As I understand it, you are looking for something like a 'transfer function' processor. You put in CV x and it outputs CV y, where y is some function of x.


For a simple tracking generator, a user might have 5 adjustment points across the range to create a complex curve. (The simplest tracking generators work much like graphic EQs, but for voltages.) With more complex tracking generators you can adjust the slope between the points to get the desired response.

Technically, you might describe those curves using a complex transfer function, but a user wouldn't be able to get to the desired result if they had to approach it from that perspective.
Videographics
brandonlogic wrote:
Mutable frames? hmmm.....


Yes, DC coupled scanner/mixer modules like Mutable Frames and Make Noise RxMx come closer than anything else I know of. With these you can kind of fake it: You mult your input voltage into the control input AND all of the channel inputs. You then feed in different voltages and try to adjust each channel level based on the adjustment you want for when that channel is selected by the input voltage at the control input. As the input voltage changes it'll output the input voltage adjusted by the level of whichever channel (or blend of channels) is being selected by the input voltage.

This'll kind of get the job done in some situations, but it's weird and kludgy enough you couldn't call it a reasonable substitute for a tracking generator.
jamos
Now that I think about this, Jurgen Haible designed one of these a few years back. it was all analog, had eight stages, and lots of bells and whistles. Now that Random Source has the rights to his designs, they would be the ones to ask about this.

I hate to say this but s tracking generator is nothing at all like a graphic eq except in the sense that they both allow the musician to create a shape. One is in the time domain and the other in the frequency domain. There is no circuit similarity.

In audio terms a TG is more like an arbitrary waveshaper.
Videographics
jamos wrote:
I hate to say this but s tracking generator is nothing at all like a graphic eq except in the sense that they both allow the musician to create a shape. One is in the time domain and the other in the frequency domain. There is no circuit similarity.


I never meant to suggest a tracking generator and equalizer would have circuitry in common. I thought I explained one is for frequency and the other for voltage levels. I only presented the equalizer analogy for those who might not otherwise be able to visualize a tracking generator interface.

Thanks for the heads up that Random Source might be sitting on a design for a tracking generator!
Videographics
jamos wrote:
Jurgen Haible designed one of these a few years back.


Found this: http://www.till.com/articles/scanner/index.html

Apparently Jurgen originally designed it to be a scanner/vibrato circuit to emulate the ones on the Hammond organs, but then he suggested it might also be used as a voltage controlled crossfader, a wavefolder with dynamic breakpoints, or a tracking generator with voltage controlled breakpoints. (With so many alternate uses, he shamelessly suggested everyone should buy at least three. hihi ) Interesting. A look through the design suggests that, because its use as a tracking generator isn't the circuit's primary design goal, it would end up working similar to an 8-stage version of some the scanning mixers discussed above. Also, it looks like the design is all or mostly there, but apparently some of the essential components are no longer available.

In the end, this is more evidence that manufacturers with a design for a scanning mixer could fairly easily transform it into a design for a tracking generator.

I'm still astounded to find none of these readily available. sad banana
cptnal
I'm thinking 4MS SMR, with its six frequency-band-definable envelope followers. In fact, the more I think about it, SMR covers a lot of this kind of ground.
Mungo
Videographics wrote:
brandonlogic wrote:
Mutable frames? hmmm.....


Yes, DC coupled scanner/mixer modules like Mutable Frames and Make Noise RxMx come closer than anything else I know of. With these you can kind of fake it: You mult your input voltage into the control input AND all of the channel inputs. You then feed in different voltages and try to adjust each channel level based on the adjustment you want for when that channel is selected by the input voltage at the control input. As the input voltage changes it'll output the input voltage adjusted by the level of whichever channel (or blend of channels) is being selected by the input voltage.

This'll kind of get the job done in some situations, but it's weird and kludgy enough you couldn't call it a reasonable substitute for a tracking generator.
I think you're focused on the specific user interface of faders to set the points. MI Frames lets you place many points spread arbitrarily across the full range using a keyframe ui with 2 knobs (one for time, one for value). The only patch is the CV in to its frame modulation input, and then you have 4 output channels that can each have a different set of values.

Videographics wrote:
Tracking generators are damn useful for all kinds of synthesis applications. So where are all the Eurorack tracking generators?!
They can be very universal functions for use in a modular, anything from a quantiser to a programmable distortion:

But its the UI that seems to be the challenge, so that module has multiple UIs on the computer to create lookup tables for different purposes.
Navs
Toppobrillo Mixiplexer is an analogue scanning multiplexer.
kay_k
that would be a nice module:

a display to edit the XY curve with two encoders and different modes for the transfer function (lin/log, min/max, S-shape/saturate and "draw") and pre/post function offset

4 channels each can have their own transfer function

Besides the GUI it would be actually very easy to make. A controller, DC coupled fast multichannel 16bit codec .. Y=look_up_table(X)
255 values would be sufficient I suppose.
If I had time for that GUI programming I'd jump on it. Never enough time tho
dooj88
how does that differ from a multiplexer? i've been keeping an eye on the Vinicius Electrik lizard module, and it seems like it does what you're describing, though they are summed to 1 output. 8 inputs, and you have 8 knobs to control the value of each input, and it scans through at a rate set by the clock (i think, depending on the mode).

description of what i'm referring to starts at 2:50, or module overview starts at 1:51

flashheart
dooj88 wrote:
how does that differ from a multiplexer? i've been keeping an eye on the Vinicius Electrik lizard module, and it seems like it does what you're describing, though they are summed to 1 output. 8 inputs, and you have 8 knobs to control the value of each input, and it scans through at a rate set by the clock (i think, depending on the mode).
Not really. A tracking generator will smoothly morph between voltages based on a input voltage. Essentially it maps the output CV to the input CV. Frames is really the only module that'll do this with up 24 'points' (I think). The Toppobrillo multiplexer and the Doepfer A144 morphing controller (with multiple vcas/crossfaders) will do it to a more limited degree.
cptnal wrote:
I'm thinking 4MS SMR, with its six frequency-band-definable envelope followers. In fact, the more I think about it, SMR covers a lot of this kind of ground.
Nope, nothing like it I'm afraid.
pelang
i built this Analog Tracking Generator from Grant Richter long time ago...works perfectly[/img]:
https://web.archive.org/web/20141015022754/http://www.musicsynthesizer .com:80/DIY/Grant/CVtwister.html

pelang
backside : )

Videographics
As everyone continues to try to think of ways to use commonly available modules as tracking generators, please be aware that tracking generators do not work in the time domain at all and they all provide smooth transitions between the adjustment values. Also, 'normal' tracking generators have a full range of linear response (no effect) with nominal settings, which I highly doubt would be possible with any of these scanner-type modules people have been posting about.

Tracking generators are relatively simple utilities that shouldn't cost a fortune. (Remember Oberheim could afford to add 60 of these to their Matrix 12 analog synth and still sold it at a competitive price.) Only super fancy ones would have more than a single input and a single output. From that perspective I'd say Disting, despite it's limited interface, is probably up to the challenge. Sliders are nice, but for this UI really isn't a big deal for me as long as I have some way of setting a few values. (The Oberheim implementation uses five knobs with a single input and output.)

pelang, thanks for linking to the Wiard / MonkeyFlux model. Cool you actually made one of these! thumbs up That picture was also linked to in my initial post but it was somewhat hidden. Here it is in-line:

fjoesz
frames can do this, right?
jamos
Videographics wrote:

Tracking generators are relatively simple utilities that shouldn't cost a fortune. (Remember Oberheim could afford to add 60 of these to their Matrix 12 analog synth and still sold it at a competitive price.)


That's because the Oberheim control voltages were all generated and processed digitally. An analog tracking generator is quite complex.

And oops - I was wrong. The Haible design http://jhaible.com/legacy/interpolating_scanner_and_scanv/jh_interpola ting_scanner_and_scanvib.html is not just a tracking generator, but an interpolating scanner. It can be used as a tracking generator but it does a lot more than that.
Triglav
So basically a Buchla 256e for Euro?
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