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Read my comment before you vote to close.

Is there an effect/vst plugin/flow that measures the rate of change of one parameter of a sound, e.g. volume, and can use that to change the amount of another parameter? (in what I'm currently working on, it would be changing the volume.)

Context: I'm trying to make something that sounds like a guitar volume swell (see this question for explanation), but through a digital effect

Ivan
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  • A couple of questions: 1) I've not heard about an existing effect that measures the rate of change of a particular aspect of sound, but if you're making a digital algorithm yourself, wouldn't it be within your power to create it? 2) It's not clear to me why to make something that sounds like a guitar volume swell, you'd need to measure the rate of a particular aspect of sound..? – Нет войне Jun 17 '21 at 17:34
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    I don't think this belongs on here at all, it belongs on dsp.stackexchange.com . Secondly - I think you mean an Envelope Follower. Google it. – Tetsujin Jun 17 '21 at 17:50
  • Depending on what DAW you are using, you can probably chain limiters and compressors and noise gates achieve some kind of effect, although there are probably better ways to achieve the swelling effect you so seek – nabulator Jun 17 '21 at 17:55
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    @Tetsujin Doesn't an envelope follower measure another parameter, rather than the rate of change of that parameter? (of course the former may actually be what the OP wants). – Нет войне Jun 17 '21 at 17:56
  • an env follower at its most basic uses in effect a gate with a variable attack [the violining thing], but added to that is often a filter, based on level. It's 'one parameter triggers another'. Another description would be 'side chaining'. I'm not really sure quite what the OP is after, whether it's some poorly-defined DAW effect plugin, or a DIY project for live guitar. – Tetsujin Jun 17 '21 at 18:00
  • @topoReinstateMonica, yes, envelope filter... and gated reverb, see my answer. – Michael Curtis Jun 17 '21 at 18:03
  • I’m voting to close this question because I agree this likely belongs on dsp.SE, but the comments make clear that at minimum it needs an update to clarify the issue. – Aaron Jun 17 '21 at 18:51
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    @Tetsujin I think this would be a dsp question if I was asking technical signal processing questions, but I think I'm just asking if a certain musical tool exists. Why I'm talking about rate of change is that's how you measure attack, it's when volume increases quickly. Googled the envelope follower, and I think it's just what I need. Thanks! Probably not ideal in all circumstances, but for this guitar thing it's good. – Ivan Jun 17 '21 at 18:59
  • @Aaron Signal processing is not about musical effects in DAWs. I don't imagine it's primarily people who use DAWs and know about plugins that browse there. This question is me seeing if a musical tool exists, not having a technical dsp discussion. – Ivan Jun 17 '21 at 19:05
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    Instead of instructing everyone to go through the extra work of reading the comments, which can be deleted in time, how about just updating your question to clarify. As mentioned in my own comment, that's what is needed. I'd retract my close vote once the question is sufficiently clear. – Aaron Jun 17 '21 at 23:55
  • @Aaron I don't see how it's unclear, other than the word "effect". – Ivan Jun 18 '21 at 01:01
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    My suggestion would be at least to update to reflect answers to topoReinstateMonica's questions. – Aaron Jun 18 '21 at 01:19
  • Why would this be a fit at DSP when the D in DSP stands for digital and the top voted answer here is about analog electronics? I’m completely lost on why this question is closed. Aside from that digital effects are on topic here. One of my more popular Q and As is about digital reverbs. – Todd Wilcox Jun 18 '21 at 12:22
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    @ToddWilcox at the time I vtc'd & suggested dsp, we didn't know quite what was being asked for. The 'vst plugin' bit was added well after that. Most of the clarification of use-case is still only in comments. – Tetsujin Jun 18 '21 at 12:44

2 Answers2

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An envelope follower uses the volume from a sound to generate an envelope signal which can then be used to control a parameter of an effect. The most popular use for an envelope follower is to control a filter to create an auto-wah effect, but there are envelope followers that feature output of the envelope signal itself to be used to control other effects.

That said, for the end result you’re looking for, I would also explore expanders and compressors. They react to volume changes with other volume changes. You could say they are envelope following effects that use the envelope to control volume. So if you can find the right time constants you should be able to make a swell.

Todd Wilcox
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    Another potentially interesting one could be a _slew limiter_, which limits the rate of change and can change a rapid step into a smooth curve, and for example make a glide/glissando from stepped pitch changes. These are available as physical/analog components for modular synths as well. And a very interesting thing to look at is Electro-Harmonix Attack Decay pedal https://www.ehx.com/products/attack-decay/ ... which might do what the OP wants. Or the EHX Superego+ pedal https://www.ehx.com/products/superego-plus/ – piiperi Reinstate Monica Jun 17 '21 at 19:10
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The one that comes to my mind, that is an actual, common effect, is gated reverb.

It's combination of noise gate and reverb. I don't really know the sound engineering of it beyond a summary. The noise gate part is based on amplitude (volume.) When the amplitude goes up high, like hitting snare drum, the reverb is applied, then when the amplitude drops down, the reverb is shut off. It's a famous effect from the 1980's applied on the snare drum for a big, fat, wet snare sound.

So, gated reverb is an amplitude parameter changing the reverb parameter.

I think envelope filters do the same thing, but with different output. They take amplitude as input (how hard you play) then change some other effect, like tone.

I imagine envelope filter would be the effect model for you to consider with your volume swell idea. Or, if you haven't looked at envelope filters before, check them out first. You may find something that already does what you're looking for.

Michael Curtis
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    Gated reverb at its most basic, original form [Peter Gabriel/Phil Collins/Hugh Padgham], is literally just a gate applied to the ambient mics. They open when it's loud & close when it's quiet. First ever appearance, Peter Gabriel's The Intruder. – Tetsujin Jun 17 '21 at 18:07