Auto Duck?

So, if I’ve read the instructions correctly, the track that needs to “duck” should be above the track with the signal trying to be heard. I’ve got that.

From this point, I’m writing my interpretation of what I think the instructions mean:

Select the upper track (the music track) and put the cursor on the ruler when you want the “duck” to start.

Click … and I get a message that “Autoduck needs a control track which must be placed below the selected track(s)”.

I’ve looked in the glossary and any other sort of likely places and I can’t find a definition of “Control Track”, or how to place it.

I tried putting an empty audio track there - no joy. so I tried an empty track above… still no joy.

The only parameter I changed was to increase the “duck” amount from the default 12dB to 20dB but I can’t imagine why that would matter. Obviously, there’s something I’m not understanding. Help would be appreciated.


I’ve never used this effect

But typically, the control track would typically be voice/narration… Whenever the narrator is speaking, the music “ducks” out of the way.

“Ducking” is when the volume of one sound is reduced so that you can hear another sound.
“Auto Ducking” is when the “ducking” is triggered automatically.

You will have heard the “Auto Duck” effect many times if you ever listen to “pop” radio.
Often the radio DJ will talk over the record that he/she is playing. As they do so, the music from the record goes much quieter, then when they stop talking the music comes back up to normal volume. That is the “Auto Duck” effect.

Using the DJ example:
The “control track” is the track that has the DJ’s voice.
The music track is the track that will be acted on (made to “duck” below the level of the voice.

In Audacity, the “control” track is placed below the “music” track. You then select the music track, and apply Auto Duck. The effect looks at the control track, and whenever it sees the DJs voice, it automatically reduces the level in the music track.

Thanks - that’s very a clear explanation. I had a problem figuring out the but once I got that, the “duck” worked. (quacked?)

having used that option (Right at …), will that apply to any sound I put on the lower track? That is, it worked for the one voice-over I had prepared but I have more to do. Can I put the rest of the voice clips in bits on that same track and have the upper track Duck at each instance, or do I need to re-Duck each time?

BTW, much impressed by the whole “duck” thing - this software constantlyamazes!

I’m not sure that I understand your question, but anyway I think much of the fun of learning something new is the element of discovery. Whatever it is that you are asking, try it out and see what happens - “experience” is the best way to learn new skills, and they say that experience comes from making mistakes (which is fine unless you are learning how to land a Jumbo jet). There’s always someone here if you get stuck.

they say that experience comes from making mistakes (which is fine unless you are learning how to land a Jumbo jet)

yeah - the variant I relate closely to is:

“If at first you don’t succeed, don’t take up skydiving!”

I’ll try adding more stuff to see if it “ducks”. Regardless, I’ll let you know.

Presumptuous question - does someone accumulate these answers and, as appropriate, use them in editing the manual/help? Seems to me you people know more about where the manual is unclear just from answering questions…

(Of course, I’ve always said that the best people to proof the manuals are people who’ve never used the software. That was me 30 years ago - I was involved in design/testing a choral music database package. The person in our group who really hated me was the guy who wrote the code - if it didn’t work the way I intuitively thought it should, I tried to get him to rewrite. Some epic battles resulted…)

Stupid follow-up question - is there some way to see (either from the code or from a quick visual check) whether the … Oh. I just read back in this thread. By definition, applying “Autoduck” means it will “duck” everytime there is signal in the “Control Track”. So 1 music track above that ducks everytime it has a signal in the track below.

Is there a “duck” command? or just “Autoduck” with parameters that allow me to control how much of the Music track will duck - i.e. I could put signal below the music that it’s not supposed to duck? Or would it have to be on a higher track (not the Control Track) and be added in in the “Mix and Render” command? (I know - it’s always the newbies who ask these dumb questions…)


Yes, time permitting. But I don’t regard Audacity Manual as highly unclear if you follow the steps in “Preparation”.

If you put too much text in the introduction, people may not read all of it. I made a minor tweak to the introduction, but you won’t see it until 2.0.7 is released.


I don’t regard the manual as “highly unclear” either but…

The term “control track” is used, but there’s no definition in the glossary. And while “control track” defines one of the two there’s no equally concise “title” for the other track.

Even the term “control track” I find vague:

  • Is the Control Track the one with the main file? IOW does it detect the presence of another track and “control” the duck? Or

Does the presence or absence of signal on the “control track” cause the main file to duck, therefore in charge (“controlling”) whether or not the main file ducks?

Trust me - I’m NOT criticizing. I know how hard it is to write this kind of documentation.

(Two Laws seem to rule:

  1. If, under a given set of circumstances, anything can go wrong (i.e. be misinterpreted) it will, and

  2. It is impossible to make anything “foolproof”. Fools are much too inventive.)

(and yes, I stole both those “rules”)

I remember back when I was a partner is a tiny software company. Writing documentation took more hours than both coding and testing combined. If I thought I could make a meaningful contribution to this project, I’d be happy to volunteer a few hours (until my wife figures out what I’m doing… )

Meanwhile, I repeat - this is a magnificent programme, it does far more (and does it far more elegantly) than I expected.


For what it’s worth, whenever I use Auto Duck, which is not very often, I can’t remember which track should be at the top and which one below, so I have to either test it to find out, or look in the manual.

“Control track” is not a standard Audacity term. I believe the term was coined by the person who wrote the effect when describing (pre-documentation) what the effect does and how to use it, or perhaps by whoever first documented the effect. Either way, we’ve not come up with a better term, so that term has stuck. The general idea of a “control track” is that it is “a track that controls something” (which is hardly worth putting in the Glossary :wink:

In the context of the Auto Duck effect, the “control track” is the track that controls how much gain (amplification / attenuation) is applied to the other track.
In the “DJ” example posted previously, the track with the DJ talking is the “control track”. When the DJ talks, the gain in the other (music) track is reduced (made quieter). The DJ talking track “controls” the level in the music track.

Regarding the documentation, I think that Auto Duck is quite a tricky effect (it’s the only effect that requires two tracks). Perhaps it would be useful if we had a step-by-step example of its usage in the wiki, and a link in the manual to that example. (as always, it’s a matter of finding the time to do that - volunteers to help documenting are always welcome)

I disagree about Wiki - we’ve just done an exercise where Audacity-version-dependent, effect-specific material was moved from Wiki to Manual.

Peter may have a view, but I would envisage it as an Examples page for that effect in the Manual.


I was thinking more of a general description about “ducking” and “auto-ducking”, what they are, why they are used, how it is done (not software specific - often it is done in hardware). I get the impression that the main problem discussed in this topic is about understanding what Auto Duck was trying to do. Once that is clearly understood then I think it becomes a lot easier to see how to use the Auto Duck effect in Audacity. Yes there could be a “worked example” (using Audacity) in the manual. Perhaps both.

I see, thanks. Is there enough to say about that, as opposed to linking to Ducking - Wikipedia ?


Probably not much more needs to be said, but it could perhaps be a bit more user friendly with some illustrations and a bit more description about how it works (without too much emphasis on “side chain” gates). Perhaps also a bit more detail about how it might be used when mixing down music (which is the focus of this article: Ducking At Mixdown)

Having reread the manual entry, and these posts, it occurs to me that all that’s really needed is a firm “naming” of the tracks. (That might not be as easy as I would like, but…) Then if we have a “control track” and “theother track” the terms, used consistently, will allow description of a series of steps that 1) place the tracks in the correct order, 2) clarify the commands used on each track (none, on one, I think) and 3) allow a cogent description of other possible functions (such as multiple “ducks” on one main track reacting to a series of events on “theother” track), how to cancel “autoduck”, etc.

But coming up with clear, unambiguous, accurately descriptive names is going to be a challenge, I fear. Best done by a group of 3 or 4 people who understand Audacity, and sound editing, (and maybe programming) sitting around a table and fighting over words. (personally, I would only get involved if someone else were providing the libations…)

(Among the “other possible functions” that I wonder about is the ability to duck the input from more than one line. For example, I have a 12 track project with 3, potentially 4 recorded sound effects that I want to trigger “ducks” at different times. I assume I can gather all the effects into one track but that will only be able to trigger “ducks” on the track directly above. True?)

So, if I want to have two tracks - one ending and one starting - and have them both “duck” a sound effect on a third track, I think I’m in trouble, no? In this case, I would have to combine music clips into one track and sound effects into the other track. That should work, but I lose a lot of the inherent versatility of having each clip on it’s own track.

Ok -there’s a lot in this post - some of it vocabulary, some of it almost a “wish list” for enhanced function (I think).

thinking this through a bit more, I have 12 clips, joining in some musical way, and 3 or 4 sound effects clips that trigger “ducks”. 16 tracks is going to be a mess to control (says the guy who thinks 4-part “a capella” is a challenge!) in a way that allows maximum “artistic” freedom and versatility.

OK - I give up - the rest of you can take over from here (“Forgive him - he knows not what he asks!”)


As the Manual says, you can have one control track (which must be unselected). You can select multiple tracks to be ducked.

So if you have material for a control track that is on separate Audacity tracks, you must select those tracks then Tracks > Mix and Render, which makes one track and removes the previous separate tracks.

Make sure that resultant track is underneath the tracks you want to affect, and make sure that resultant track is deselected.

You could instead Tracks > Mix and Render to New Track, which would create a combined track but also retain the previous separate tracks.

But yes I guess you have a feature request.


The way that I would do that is:

  1. Select the tracks that I want to use to “control” (trigger) the ducking.
  2. “Tracks >Mix and Render to new track” (Ctrl+Shift+M)
  3. Rename the the new (mix) track as “Control” or something equally meaningful.
  4. Mute the “Control” track.

Interesting point: The Auto Duck effect works on the “track waveform data”. It takes no notice of pan, gain or mute.
Now you have a “control” track that you can use for triggering the duck but the control track will not be heard when you play (because it is muted). You also have all of the original audio clips on their original tracks - they will be heard when you press Play because they are not muted.

Tracks may be moved up or down as required to achieve the required ducking effect (for moving tracks, see: Audacity Manual)

As previously described, muted tracks are not included in the exported file.

Steve and Gale - Thanks for your responses.

It’s very possible that I have not read the manual accurately enough - if so, I apolgize - but it seems that working on a project of any complexity could get crazy very quickly.

I start with 14 tracks - the source for the “music medley” - Then I add the sound effects tracks (3 is the number for the example). (For this, I’m going to use the terms “source track” for my original recording, “effects track” for the sound effects or dialogue that the music is making way for, and “results track” for the output from a “mix and render”.)

So, if I want a sound effect for where track 3 yields to track 4 (regardless of how I blend them), I do a “mix and render” of source 3 and source 4, which produces Results Track 4A. Immediately below Results Track 4A I have to have Effect A.

Mute 3 and 4. Set 4A to autoduck for the length of Effect A.

Repeat more or less for Effect B and Effect C.

If I’ve imagined this correctly, in the above example I’m going to end up with 19 tracks! - 12 source, 3 effects, 3 results, all mixed down to 1 output track. And I don’t think any of the Effect tracks can be combined.

If someone out there can review this to see if I’m close, I’d appreciate it.

Roger (who now has a headache…)

The project can be as simple or complex as you want :wink:
In other words, it will need to be as complex as it needs to be.

At any time, you can reduce the number of tracks by combining tracks into a fewer number of tracks.

There are several ways of combining tracks.

  • “Mix and Render” will “mix down” all selected tracks into a single (mono or stereo) track. The original tracks are deleted. Spaces between audio clips are replaced by silence. The “mix” track is one continuous audio clip.
  • “Mix and Render to new track” is the same as “Mix and Render” except that the original tracks are not deleted.
  • Audio clips can be dragged from one track to another (using the Time Shift tool. Empty tracks can then be deleted by clicking on the [X] in the top left corner of the track. Mono clips can only be dragged to mono tracks and stereo clips can only be dragged to stereo tracks.
  • Audio clips can be copied / pasted from one track to another. Stereo clips can only be pasted to stereo tracks, but mono clips may be pasted to mono or stereo tracks.

Thoughtful management of audio clips can massively simplify complex projects.

So have I got this right:
Tracks 1 to 14 contain musical audio clips that will eventually form the “music”. You are referring to these as “source tracks”.
Tracks 15, 16 and 17 are sound effects. You are referring to these as “effects tracks”.
Additional “mix” tracks may be added in the course of working on the projects, which you are referring to these as “results tracks”.

You’ve lost me. I don’t know what you mean.

Steve: thanks for your patience with this. I decided to start a new thread with this - it’s liable to get confusing…

I have 3 tasks. (I’m avoiding the word “project” since it has a specific meaning in Audacity.) Currently dealing with the first task - a 30 minute “broadcast” purporting to come from a 1947 radio studio. (This will play while the reallife/currenttime audience comes in and settles.)

So - I have clips of period recordings, a couple of period ads, and I need to record a couple of “station id’s” etc.

Since I am neither the Producer (my wife is) nor the Director (her friend is) I have to guess exactly what they want - and keep everything flexible so I can change it severral times.

In my first attempt, I combined all the songs on to one track (by hand). As soon as I saved it, it became one long file and the clips were all joined. Moving them around, manipulating the transitions, adding more material, etc became difficult.

So, after reading some more and asking questions here, I put all the songs (each in their own tracks) into a new file. Then I added the ads. (I had to shift songs down the time line to make space but that was ok.)

Then I worked on transitions - fade in, fade out, etc. That was good too. By now I’m up to about 16 stereo and 3 mono tracks.

Now come the "voice over"s. Opening “Good evening and welcome to…”, a couple of station id’s, maybe some song credits and “forecasts” (“That was ccndsofr singing akowfj. Next, for your listening pleasure, we have jkesfda; and his whistleing chimps” - stuff like that) This is where “Autoduck” comes in.

Of course, I’ve never used Audacity before (quite literally!) and the term “Autoduck” amused me greatly - until I tried to line up the various tracks! I have recommendations for how/when to “mix and render” (until now I thought that was a cooking term!), mute and unmute different tracks, etc. etc.

All the while keeping all my options open to be able to adjust to what “she who must be obeyed” and her friend the Dictator - oops, sorry, Director - decide it “should” be.

I have a sense that pre-planning the order of all the tracks - music tracks, ad tracks, “mix/rendered” tracks, voice over tracks, more “mix/rendered” tracks - so that the tracks that trigger “ducking action” are directly below the tracks that are to “duck” is crucial.

Fortunately, I have a couple of weeks. I think I’m going to need them!

So I plead for patience from all - for badly worded questions and explanations, for repeated requests for clarification, for combining too many topics into one thread. This is a huge challenge for me - and the outcome may have a significant impact on my marriage!

On the positive side, if I can get through all this, I should have enough material and comprehension to write a decent tutorial…

Note: none of my comments are intended in any way to criticise what is already on the site. I am so new to all this that answers that seem obvious to more experienced users have to be spelled out for me.

And the technology has changed everything. When I made my own first “mixed tapes”, it required the actual, physical cutting and splicing of bits of acetate. (My first attempt at that failed miserably when I actually spliced a chunk in backwards… )

Thanks to all for patience and understanding.

<<Steve wrote:

Roger Priddle wrote:I start with 14 tracks - the source for the “music medley” - Then I add the sound effects tracks (3 is the number for the example). (For this, I’m going to use the terms “source track” for my original recording, “effects track” for the sound effects or dialogue that the music is making way for, and “results track” for the output from a “mix and render”.)

Steve wrote: So have I got this right:
Tracks 1 to 14 contain musical audio clips that will eventually form the “music”. You are referring to these as “source tracks”.
Tracks 15, 16 and 17 are sound effects. You are referring to these as “effects tracks”.
Additional “mix” tracks may be added in the course of working on the projects, which you are referring to these as “results tracks”.>>

Sorry - this is badly clipped from the original conversation…

I think part of my challenge with Audacity, especially when communicating with the rest of the community, is the fact that I don’t know what the “proper names” are for identifying various “classes” of tracks. I have looked around, but not seen definitions - maybe they’re there and I’ve missed them, in which case I appologize - but it seems to me that if we’re all using the same words to mean the same things, we’d be better off.

I didn’t have this problem when working on “simple” projects, but the current project is driving me nuts, especially since I need to keep completely flexible at each stage. So, until there’s an “UnMix and UnRender” command , I have to keep all the tracks separate. And I have to be able to refer to each “type” of track.

So far, I appear to have at least 4 distinct “types” of track. I have the one that is brought in from an original pre-recorded musical source. Then I have an area where two “original pre-recorded musical tracks” either butt up or overlap. This is distinct (I presume) from an area where two or more tracks are combined using “Mix and Render”. And what is the proper name for the end product of a “Mix and Render” when the result ends up on it’s own track? “Mix track”? “Result track”?

Then I have a “sound effect” that has to fit in either between sections of a track or under a section of a track. And a pre-recorded sound effect is different from a piece of dialogue, etc. etc. etc. (Although, I guess, they could be treated as the same type… But should they have a unique, identifying term?)

I am NOT trying to be difficult but these are all (admittedly minor) points that have come up that have needed “clarification” for me one time or another. If I am the only one, I’m sorry and will now slink off into the darkness.

But if I’m not the only one, maybe there could be a concensus “Naming of tracks” document to help people use agreed-upon terms to help describe issues and solutions. (In reviewing this, it occurs to me that there probably ARE agreed-upon terms - every professional field has it’s own jargon. It’s just newbies like me who need the distinctions spelled out…)