Real time VST and undo effects

Hello friends. I looked new version. I have not found how to undo overlay effects. Really there is no history? If it is, please tell me about it. Ability to make the abolition of the very important. I will not mention the real time. Share a link where you can write to the developers. From the site does not pass. I hope for an answer. Thank you.

Audacity 2.1.1 may be downloaded here:

Edit > Undo or CTRL + Z.

View > History… . History persists until you close the project window.

Real time preview is available in 2.1.1 for most effects except Nyquist effects and built-in effects. See


The next version of Audacity will have real-time preview for two of the built-in effects, Wah Wah and Phaser. Real-time preview will be added to more built-in effects in due course.

(interpreter) Hello. Thanks for the answer. This sense of history in order not to cancel the effect of the latter, and to be able to cancel any effect. Without this feature, it is very difficult to do quality work. In the process, I want to reduce such an equalizer, and can not do, if there is no history of the overlay. That’s what I wanted to write to the developers.

If I understand your meaning correctly, Audacity is the wrong sort of program for your needs. It sounds like you want a “real-time DAW” application, such as Reaper, Cubase, Sonar, or similar rather than an audio editor like Audacity.

(translator) o Audacity good free program! Work in real-time is too big a request for free :slight_smile: No history of work with the TSA until this one which makes the lack o audacity. I hope that for the developers it will not be a problem to make such an addition. It’s really important. I know SONAR… . How to write to the developers? The website link is not working?

This is what I think you mean:

You apply “effect 1”, then “effect 2”, then “effect 3”.
The history shows:

  • effect 1
  • effect 2
  • effect 3

To undo “effect 1” you need to undo “effect 3”, then undo “effect 2”, then undo “effect 1”.

I think you want to undo “effect 1” without undoing the other two effects.
Am I correct? Is that what you mean?

And not just effects. If I apply a compressor and then Analyze > ACX Check, the system insists on backing out of ACX Check before uncompressing. That’s not inconvenient, that’s just silly.


Yes, that’s right. Just the language barrier and the translation may not be correct).

Professional editors have full ability to change all and at any time. And in our audacity at least was able to CANCEL and apply again. So to edit any effects. To do less bass on track 5. Change the reverb on 4 …

But if I have 10 tracks! No one can handle them 100% so well, so as not to make the correction. If our audacity does not give real-time, should be able to override any overlay plugin. Otherwise for professional purposes this is not real. This one what does for me personally the difficulty our audacity. Really like that the developers added this feature. They even export done in 32 bits. The noise is to remove good. Reverb. good.

That is presumably because there is no way in a Nyquist plugin to tell Audacity not to add the effect to the undo stack.


The link is working There is no real point writing there because we can count “votes” for requests here, which the developers can look at.

You can vote if you want for “Non-destructive (non-linear) editing”, perhaps something like bolted onto the existing Audacity procedures.

If you want to vote for what amounts to a “non-destructive DAW”- do not change the original audio data and do not store the processed audio until until it is “rendered” into a “mix” file, well you can vote but I guess it is not going to happen.


there is no way in a Nyquist plugin to tell Audacity not to add the effect to the undo stack.

The “event.” It’s not an effect. That’s my objection.

I understand your point koz, but “technically” it IS an effect, which is why it behaves as it does.
It would only take a very small modification to the Nyquist script to make it write its output in a label, in which case I think you would agree that “Undo” would then make sense.
Audacity does not know if the " ACX Check" effect will return labels or not until the effect has been run, so to not log running the effect in the Undo History, Audacity would have to check the return value from the effect and treat it as a “special case” if the return value is not audio or labels. Currently this is tricky to do because the “flag” that determines whether to log the action is set when the effect is called, but at that stage Audacity does not know whether the effect will modify the project. Audacity only knows if the project has been modified after the effect has run.

I think I can see how this could be changed so that ACX Check does not get added to the Undo history.
The general case here is “If an effect does not change the state of the project, it should not be added to the Undo history”.
If Gale agrees that this is a bug, then I ‘may’ be able to fix it.

I guess you could call it a P4 bug. The ACX undo is a no-operation except it may change the selection, which is probably not very helpful either.


There are a few other “no op” Nyquist plug-ins, though we don’t currently ship any of them.

What about the “Get Noise Profile” step in Noise Reduction? It does not affect the project, and Undoing does not undo the profile. I don’t think that it would be useful to undo the profile, so perhaps better to treat that as a “no op” effect?

That’s a bug in the plug-in, but we don’t track bugs in plug-ins that are not shipped.

Undoing the Noise Profile is not useful now, but might it be useful if in future we allow multiple noise profiles to be stored?

Also if capturing the Noise Profile is made a no-op, would “Repeat Last Effect” still be available after capturing the noise profile, so that you could apply the captured profile at current effect settings without reopening the effect?

You mean it’s a bug given it does not change the project state?

Is there not a strong case to ship the ACX plugin?


No it wouldn’t. “Repeat Last Effect” repeats the last effect in the History.
That’s a good argument for keeping “no op” Nyquist effects in the History., so perhaps we don’t want to call it a bug.

It also opens another question - why don’t we have “Repeat Last Effect” for Generator and Analyze effects?

I think there is a stronger case for ACX Check (and other analyzers that just show information) not to be in the Undo Stack than a case for making Noise Profile no-op. Even if we had Repeat Last Effect for Analyzers, would that be more useful than just setting a direct shortcut for ACX Check?

Interestingly, showing Help in Vocal Remover is (correctly) already a no-op.

What would Repeat Last Effect in Generate and Analyze menus do - repeat the last of any effect, generator or analyzer, whichever menu it was called from? Calling it “Repeat Last Effect” could be ambiguous, even though it is clear what will happen once the item is active. Perhaps it would be called “Repeat Last Plug-in”?

Another option would be that we had Generate > Repeat Last Generator and Analyze > Repeat Last Analyzer, with separate shortcuts from Effect > Repeat Last Effect (which would be the last process effect run). That would be the most flexible, if we can afford the shortcuts.


That is a side effect of it being a “process” type effect. “Process” effects are intended to “process” audio, so the returned value is expected to be the processed audio. If a process effect does not return audio, then the “success” flag is set to “false”. Because the flag is false, the effect is not pushed onto the History stack. This does not apply to “analyze” type effects because it is perfectly reasonable for such an effect to return text, labels or numeric values.

I thinks so, yes, just as it is more useful to have Repeat Last Effect for “Effects” even though we can set shortcuts.

Having looked a bit deeper, I think that it should be possible to keep “Get Noise Profile” off the Undo History but still available for “Repeat Last Effect”.

“Get Noise Profile” is a bit of a strange case really - although it is part of a “process” type effect (Noise Reduction), it is much like an “analyze” effect in that it analyzes the audio selection and does not return processed audio.

Yes, I was thinking of separate shortcuts for Generate, Analyze and “process” type effects (though right now I don’t know how that would be coded).