# Is it possible to invert the mid and side channel of an audio?



## fan455 (May 7, 2022)

Hi, I'm new to audio mixing learning. I have a piano audio that sounds drier on the side channel but wetter on the mid channel. My reference track is just on the contrary, and it sounds way better to me. So are there any approaches or plugins that can inverse the mid and side of an audio? Or any other solutions? Thanks!


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## sumskilz (May 7, 2022)

You can make the sides part of the mid by narrowing the panning, or going completely mono, but the mid is already on both sides, it's just that it is the same on both sides. In other words, the sides are what is different on each of the stereo channels, whereas the mid is what is the same on both the stereo channels. The mid and sides aren't actually different channels, unless you're talking about mic positions.

To accomplish what you want, you could split the mid from the sides, and use an envelop to reduce reverb on the mid, and then use a stereo reverb on the sides, but it's not something I've ever attempted, so I can't recommend a particular plugin. I also suspect it would sound unnatural, which you may or may not be okay with.


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## fan455 (May 7, 2022)

sumskilz said:


> You can make the sides part of the mid by narrowing the panning, or going completely mono, but the mid is already on both sides, it's just that it is the same on both sides. In other words, the sides are what is different on each of the stereo channels, whereas the mid is what is the same on both the stereo channels. The mid and sides aren't actually different channels, unless you're talking about mic positions.
> 
> To accomplish what you want, you could split the mid from the sides, and use an envelop to reduce reverb on the mid, and then use a stereo reverb on the sides, but it's not something I've ever attempted, so I can't recommend a particular plugin. I also suspect it would sound unnatural, which you may or may not be okay with.


Thanks for detailed reply. So I can try to narrow the side and expand the mid, and re-combine the mic signals.


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## Lionel Schmitt (May 7, 2022)

phase invert seems to swap mid/side against each other. Mid then controls the side and vice versa, which can be good to adjust because it can make things super unnaturally wide, turning down mid (which has become side) helps. There is left and right phase - don't know much about that but they seem to do the same thing, I'd just play around with it and see what works. https://pressplay-music.com/stereo-helper/


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## sumskilz (May 7, 2022)

fan455 said:


> Thanks for detailed reply. So I can try to narrow the side and expand the mid, and re-combine the mic signals.


Yeah, but keep in mind there is no way to actually expand the mid except making it artificially stereo. Although, stereo reverb on the separated mid may be good enough to accomplish what you want.


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## fan455 (May 7, 2022)

Here're the details. I use Pearl Concert Grand which offers 4 mic signals (close, pedal, stage, hall). I analyzed every mic and found:

distance from the piano and reverb
hall>stage>close>pedal

left and right channels difference (stereo width?)
stereo mic: close>>stage>hall
mono mic: pedal

For close mic recording, the user manual says two microphones were placed on the two ends of the piano keyboard, so higher notes sound louder on the right channel and lower notes sound louder on the left channel. This resulted in a big difference between the left and right channels.

My target is a drier (closer) sound on the mid channel and a wetter (further) sound on the side channels. The pedal mic should be tweaked in a much lower volume because it has a loud key attack sound.

@CGR Hi Craig, how would you mix the mics of Pearl? Thanks!


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## gamma-ut (May 8, 2022)

You basically want to wind up with two stereo pairs from those mic signals and narrow the stereo image on the closer mix - to simulate a single mic close to the piano - while (possibly) widening the stereo image on the far pair. Watch out for phasing if you choose widening.


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## fan455 (May 8, 2022)

gamma-ut said:


> You basically want to wind up with two stereo pairs from those mic signals and narrow the stereo image on the closer mix - to simulate a single mic close to the piano - while (possibly) widening the stereo image on the far pair. Watch out for phasing if you choose widening.


Yeah, I would like to narrow the close mic signal (which is easy), and use stage and hall mic for wider image . For stage and hall mics, I'm considering two ways (which are more uncertain):

-Pan stage mic to the left and hall mic to the right.
-Use stereo imager.


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## icecoolpool (May 8, 2022)

I think I can help!

For this example, I´ve started with a stereo file that had a lot of close information on the left channel and a lot of room information on the right channel. I converted this into a DUAL MONO file. I panned the left channel into the centre. The right channel was also panned centre but I inserted a plugin that inverted the phase of the right channel. This sounds terrible on its own, but once played back with the centre channel it sounds fine. 

This is essentially an in-the-box version of the mid/side recording technque and can be used to centralize close information that is panned wide. Here is a quick before and after to demonstrate this process in action:


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## gamma-ut (May 8, 2022)

fan455 said:


> Yeah, I would like to narrow the close mic signal (which is easy), and use stage and hall mic for wider image . For stage and hall mics, I'm considering two ways (which are more uncertain):
> 
> -Pan stage mic to the left and hall mic to the right.
> -Use stereo imager.


The stereo imager is probably going to work better, and I’d be inclined to use it on the stage signal. The hall will have a lot of reflections so may just sound a bit odd if widened additionally, so mix that in after.


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## fan455 (May 8, 2022)

icecoolpool said:


> I think I can help!
> 
> For this example, I´ve started with a stereo file that had a lot of close information on the left channel and a lot of room information on the right channel. I converted this into a DUAL MONO file. I panned the left channel into the centre. The right channel was also panned centre but I inserted a plugin that inverted the phase of the right channel. This sounds terrible on its own, but once played back with the centre channel it sounds fine.
> 
> This is essentially an in-the-box version of the mid/side recording technque and can be used to centralize close information that is panned wide. Here is a quick before and after to demonstrate this process in action:


Thanks. The after audio sounds more central. I just have some confusions. How did you pan a single channel (I thought panning was a multi-channel concept)? And how many degrees are your phase inversion?


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## fan455 (May 8, 2022)

Here's an interesting plugin I just found that could be a good solution to me. Free trial is available.









DrMS - Mathew Lane


DrMS Focus on your stereo field.DrMS is a unique spatial processor plugin, with a wide range of appl




www.mathewlane.com





From the manual, it says:

The FOCUS section uses original mid-information to create new side-information in the final stereo output.

The FIELD section uses original side-information to create new mid-information in the final stereo output.


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## gamma-ut (May 8, 2022)

It's a great little tool but I don't think you need it in this instance. You probably need to experiment a bit more with the mic selections and perhaps treating the room mics with a little delay on one side or just different mix balances. 

It would probably help if you say which DAW you're using. Logic has handy tools like the Direction Mixer, for example.


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## fan455 (May 8, 2022)

gamma-ut said:


> It's a great little tool but I don't think you need it in this instance. You probably need to experiment a bit more with the mic selections and perhaps treating the room mics with a little delay on one side or just different mix balances.
> 
> It would probably help if you say which DAW you're using. Logic has handy tools like the Direction Mixer, for example.


I use Cubase Elements, maybe more limited compared to Logic Pro.


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## gamma-ut (May 8, 2022)

fan455 said:


> I use Cubase Elements, maybe more limited compared to Logic Pro.


A quick search turns up this: https://steinberg.help/cubase_plugin_reference/v9/en/_shared/topics/plug_ref/stereo_enhancer_r.html

The help isn't very clear, but it looks as though you should be able to turn the first knob to the left to narrow the close mic stereo pair down towards mono. You may find that the other mic pairs seem open to up a bit – it's a common illusion in mixing: when everything is wide, nothing sounds like it is.

If not, Ozone Imager is free I think and there are some other free stereo tools out there before you even have to think about paid plugins like Waves S1 or DrMS.

Also, I had a quick look at the Pearl manual - I don't have it - but it surprised me that Impact wouldn't have put some control in there for stereo image. They are usually pretty good at scripting for instruments. And they did: there should be a width control over each mix channel in the instrument itself though I don't know how close to mono the close signal gets with it turned right down.


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## fan455 (May 8, 2022)

gamma-ut said:


> A quick search turns up this: https://steinberg.help/cubase_plugin_reference/v9/en/_shared/topics/plug_ref/stereo_enhancer_r.html
> 
> The help isn't very clear, but it looks as though you should be able to turn the first knob to the left to narrow the close mic stereo pair down towards mono. You may find that the other mic pairs seem open to up a bit – it's a common illusion in mixing: when everything is wide, nothing sounds like it is.
> 
> If not, Ozone Imager is free I think and there are some other free stereo tools out there before you even have to think about paid plugins like Waves S1 or DrMS.


Yeah, I actually used it. I don't think I need any other stereo imager plugins since I can use this stock gem. Though the effect itself is very nice, it alone can't solve the issue for me because Pearl Concert Grand's stage mic (my choice of the loud volume mic in the mix) has a stronger key attack on the side channel and a weaker key attack on the mid channel. I analyzed some piano recordings by _Deutsche Grammophon_ and found they're just the opposite, so that's my target. You can see purely widening or narrowing the signal would fail to exchange the key attack strengths between mid and side.

Besides DrMS, having a mid-side encoder-decoder (the MSED by Voxengo is free), plus the stereo imager, may work for me too.
(1) Seperate the mid and side channels from L/S input of Pearl's stage mic.
(2) Dual mono the side channel.
(3) Dual mono the mid signal, then apply some stereo widnening.
(4) Combine the signals in (2) and (3) into one stereo track.


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## icecoolpool (May 8, 2022)

fan455 said:


> Thanks. The after audio sounds more central. I just have some confusions. How did you pan a single channel (I thought panning was a multi-channel concept)? And how many degrees are your phase inversion?


The mono file is just placed in the centre. That´s the default position on the pan-pot for an audio file in your DAW. I inverted the phase 180 degrees on the right channel only of the right mono file which creates stereo width. By doing this I turned the left channel into the mid and the right channel into the side channel. This can be a useful technique when wanting to centre "in-situ" recorded instruments.


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