Control signals between virtual instruments

[davidka]

After checking the RePro slides, one thing which I noted was the Audio-rate CV in/out function to be implemented.

I think it is really interesting, can anyone enlighten me the current limitations and possibilites on this topic? Things such as - why isn't it widespread to connect 2 different plugins and use each others' modulators using audio rate modulation? What issues must be overcome to ensure that plugins can be stitched together like for ex. a Microbrute + Doepfer in the hardware world?

[EvilDragon]

For connecting with hardware synths y<ou need to have an audio interface that doesn't have DC coupled outputs (which is basically a highpass filter that filters very slow changing signals). There aren't an awful lot of them (MOTUs are good for this, I hear). Or you could use digital outputs (SPDIF, ADAT) via Expert Sleepers module.

Urs also mentioned that some DAWs (Logic) have issues regarding routing CV through them, can't remember details or find his post saying that ATM...

[Urs]

The biggest challenge is host support for multiple ins and outs. Multiple outs is supported kind of okay-ish-ly, but inputs for instruments is a difficult soil.

The biggest issue is, CVs only really make sense in monophonic synths. Hence you won't find many polysynths (analogue or digital hard or soft) that have CV connectivity.

I do fancy the idea of setting an example with RePro-1 - either use as monophonic synth with mono output, or use as CV eating and spitting monster within a modular environment. But also, both Native Instruments and Ableton have shown similar setups during Superbooth, so maybe it's the next big thing anyway.

Also, what ED says. For hardware connectivity you need Expert Sleepers stuff and he's coming out with a USB-solution soon.

[davidka]

Yes, I was more curious about the software part - how can different plugins be connected together.
Am I naive if I think a 'virtual' CV splitter could be used for polyphonic stuff?
If I'm not mistaken, most of the polyphonic virtual synths offer only the pitch/cutoff variations between each voice anyway, offsets can be handled by a 'voice' modulation source, or a panel similar to Diva's voice control

[lectrixboogaloo]

So, you are thinking about sending cv over the regular vst audio in and outs?

[Frantz]

Yes, I was more curious about the software part - how can different plugins be connected together.

I don't think there is standard support for this in the VST format.

The closest examples that I can think of in the software world are Propellerheads Rack Extensions and Softube Modular.

[justin3am]

I've done this with instances of Reaktor and Silentway. Also with Urs' Zebrify (the inputs pass DC, so it can receive control signals, works well with the XMF and FMOs). It's just not very practical when you are trying to use many modulations signals and route them each to several destinations. Using modular VST hosts which can run as VST in other software helps but it's still not as practical as it could be.

I'd say experiment with sending control signals to anything that has an envelope follower as a modulation source. You'll need to give up an input for the control signal, so you'll mostly be working in mono. I experimented with sending control signals to sidechain inputs on some compressors/gates and was able to effectively use some as DCAs. Others seemed to filter DC signals, so they didn't work. I can't remember which plug-ins I tested anymore.

Is it weird that I cringe every time someone refers to signals which are happening inside the computer, as "CV"?

Edit: Oh yeah, the envelope followers often rectify their inputs, so bipolar signals may act funny.

[Urs]

Well, another issue: Control signals are not necessarily pleasant to listen to. If a synths outputs a mod signal through an audio bus and the user isn't prepared for what's coming and accidentally routes it through the speakers... might be a taxing experience.

In Logic for instance all outputs of a multi-out AU that are not connected to an auxiliary channel are routed to the main output of the instrument automatically. For this reason one can't just make a fixed set of outputs. One has to let the outputs default to silence.

[zerocrossing]

Is it weird that I cringe every time someone refers to signals which are happening inside the computer, as "CV"? .

Maybe it stands for "Computer Value?"

This is one of the reasons I picked up a Scope system. Inside it's DSP world there aren't these kinds of barriers, though I don't think there's a way for it to communicate with the outside world except for MIDI and OSC. Many of the Scope instruments do take audio in and it's very simple to route anything anywhere. Some of them even work within the Scope Modular environment.

But this kind of siloing is also one of the reasons why I've never dove into a modular system. The idea that all modules don't also react to MIDI or OSC seems kind of stupid. Why shouldn't I be able to control multiple Eurorack modules all at the same time using Obscurium? I guess I could get a Silent Way set up but to me it feels like a bridge between two countries that are actually part of one land mass.

[davidka]

I've done this with instances of Reaktor and Silentway. Also with Urs' Zebrify (the inputs DC coupled, so it can receive control signals, works well with the XMF and FMOs). It's just not very practical when you are trying to use many modulations signals and route them each to several destinations. Using modular VST hosts which can run as VST in other software helps but it's still not as practical as it could be.

I'd say experiment with sending control signals to anything that has an envelope follower as a modulation source. You'll need to give up an input for the control signal, so you'll mostly be working in mono. I experimented with sending control signals to sidechain inputs on some compressors/gates and was able to effectively use some as DCAs. Others seemed to filter DC signals, so they didn't work. I can't remember which plug-ins I tested anymore.

Is it weird that I cringe every time someone refers to signals which are happening inside the computer, as "CV"?

Edit: Oh yeah, the envelope followers often rectify their inputs, so bipolar signals may act funny.

My bad, was not my intention to cause anyone feeling weird by an incorrect term - fixed the title.

I'm interested how Slate's VCC mixbuss modules are interconnected to form groups.

[justin3am]

In Logic for instance all outputs of a multi-out AU that are not connected to an auxiliary channel are routed to the main output of the instrument automatically. For this reason one can't just make a fixed set of outputs. One has to let the outputs default to silence.

Interesting... in that case, I guess it's better to use a modular plug-in sub-host to handle control signal routing.

I used to use Pluggo quite a bit and the bundle included some neat utilities for routing audio and control signals between instances and tracks.

[justin3am]

My bad, was not my intention to cause anyone feeling weird by an incorrect term - fixed the title.

No worries, I was just being silly. I've never really been fussy about terms, when the context is clear.

[Taika-Kim]

I was about to start a thread about this, I'm happy it's in the plans! I was thinking of having just a bunch of audio outputs in Bazille for example, and just output the signals through Expert Sleepers stuff to Eurorack or whatever can eat the signals.

CV in does not seem that interesting to me, but using the VST stuff for LFOs, envelopes, etc can save loooots of money. I don't even have LFOs and just one envelope in my rack!