?stereo to mono, keeping the highs from each side?

Have several contemporary stereo radio shows which sometimes have actors speaking in only one channel. There’s a mix of background sounds, music, fx going on. I’d like to make them mono, but when I do the simple method, the audio gets a little muffled. I could manually go thru the dialog and select the actor’s mono parts and highlight them to be on both channels, but that would take forever. Is there an automatic way to merge both channels so whatever the louder channel is (in a given moment) will dominate the output? Like a more flexible audio ducking?

How are you doing that, with “Stereo Tracks to Mono” from the “Tracks” menu?

Another way would be to click on the track name, then select “Split to Mono”. This will split the stereo into two mono tracks - one from the left channel and one from the right. Delete the track that you don’t want (click on the in the top left corner of the track).

Yes. Also used Nero by simply saving the audo as a mono track. Identical sound results - a little muffled compared to the stereo (as the waves must be canceling each other out or getting averaged).

Except that this totally defeats my stated goal - to keep the louder of the two audio channels at a given moment.

Maybe we should inspect your words. “Muffled” in my mind means the volume is OK, but the sharpness, sparkle and crispness is damaged or missing. You appear to be using the word to mean the performer’s volume decreased.

If the latter is the case, then you might be a candidate for Chris.

Chris’s Compressor

Chris developed a volume compressor that gracefully evens out volume variations within a show.


No, there is no automatic method.

Even if there were an automatic method it would be unlikely to work effectively. It would either need to “switch” from one channel to the other, or “fade” from one channel to the other. “Switching” would produce some strange effects if the two channels are of similar volume but with significantly different sound. “Fading” would reduce the weirdness of switching, but if “mixing” the channels is unacceptable then the same problem would occur during each fade.

To avoid the destructive interference when converting stereo to mono, resulting in loss of high frequencies, two ideas come to mind …

  1. Put the tracks very slightly out of sync by advancing one of the tracks by a few samples before converting to mono.
    or 2. applying a minute imperceptible amount of random pitch modulation to one track, this would put them out of phase and avoid the cancellation.

David Sky’s random pitch modulation plug-in attached … NB: if applied to a stereo track David Sky’s random pitch modulation applies different degrees of randomness to each track : they randomly go in and out of phase.
randompitch.zip (597 Bytes)

kozikowski, while the averaging from stereo to mono does lower the volume a tad, I meant the former interpretation - the the higher frequencies are deadened (deadened in general, and dialog is sometimes muffled (drowned out/overcome) by sound effects). However, I’ll check out Chris’ plugin since it sounds useful in general.

stevethefiddle, I agree, I can see how an automatic method feature probably wouldn’t work… But there might be a combination of effects that can be used to get the end result.

Trebor, I understand the gist of your suggestions, but don’t know what “advancing a track by a few samples” means or how to do it.
I tried changing the phase, but the mono result sounded echoey. I’ll try the randompitch plugin.

I should have said retard rather than advance :blush:
Split the stereo into dual mono, then add (“generate”) a few samples of silence at the start of one of the mono tracks.
Try adding 2 samples if you are using 44100Hz sample rate, so that would make the tracks 1/22050th of a second out of sync: too brief to sound “echoey”.
If your 11KHz sounds were exactly out-of phase, (anti-phase) and cancelling out completely, they will be in-phase after the addition of 1/22050th :
you will have constructive not destructive interference at 11KHz and the sound will be more trebly.

Re: stereo to mono

I’ve found a free VST effect which does this called “mgMono” and it works on Audacity …


  1. it’s free
  2. it does what it says on the tin.


  1. It is supplied as a RAR file so you’ll need RAR decompression software.
  2. This mono-ize plug-in it is VERY slow: on my computer it takes longer than real-time to mono-ize a stereo track, (e.g. 4min to convert a 3 min track to mono).
  3. It is labelled “alpha” i.e. a prototype, (but seems to work OK).
  4. Windows only.

Attached is a mp3 of a “before” and two “afters“. The stereo before has a distracting L-R breath effect at 2.0 -2.5 seconds, probably due the performer turning their head from one mic to the other. Mono-izing gets rid of this breath effect.

The first “after” uses my technique of shifting the tracks out of sync (here by 20 samples) before performing “stereo track to mono”, the result it does have a hint of reverb to it as a consequence of this 1/2000th of a second shift.
The second “after” (after second bleep) is mono made using the “mgMono” VST effect described above , it has exactly the same frequency content as the stereo original, ( my out-of-sync method alters the frequency content ).

“IZArc” is an excellent free archiver program for Windows and supports RAR (and lots of other compression formats). http://www.izarc.org/
It’s one of the first programs that I install on a new Windows machine.