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What does it mean if an element in a mix is in the "side" AND "mid" channels

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What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby armans » Wed Nov 18, 2020 6:43 pm

I am learning about panning and checking a mix trying to understand the panning being used in a particular song. The Verse of the song has a guitar that appears to be almost completely right panned with only a bit of signal coming through on the left channel. However in the chorus the guitar on the left comes in and the guitar can be heard both on left and right channels. Now the part where I get confused is the following. In my DAW, where I imported this song to reference, I open a plugin on the track by Voxengo which allows me to audition Mid and Side channels independently and when I try to listen to the "mid" channel the guitar is still there, but ALSO, when I listen to the "sides" channel the guitar is also there. If the guitar was centre panned in the chorus then it should dissapear when the side channel is being auditioned and if the guitar is double tracked or recorded in stereo, most of it would dissapear as the signals would be almost identical so how is it possible the the guitar is perfectly audible in both mid and side channels? Especially on the side channel the guitar is perfectly audible with no cancellation whatsoever.

thank you!
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby CS70 » Wed Nov 18, 2020 7:08 pm

Panning controls left and right, and - while related - it's not the same as mid/sides.

Both L/R and M/S consists of two channels of audio, but while L/R is about left and right (and the pan controls affect that), M/S is about capturing a signal from the front and on the lateral sides of a source.

Think of having mic pointing at a singer and another pointing at the walls to the side of the singer (and since you want to point both walls you need a figure-8 microphone with two identical lobes, each pointing at one wall). You'll have two mono signal, one capturing the singer directly, one capturing the combination of the signal bouncing from the side walls.
It's a bit of a trick as a figure 8 mic is able to "see" two sides and mix them in a mono signal - so even in this case you'll have two mono signals, front and sides.

In M/S if you remove the S you're left only with the mic pointing at the singer, and if you remove the M you're left only with the "summed" figure 8.

You can always transform between the two and if you take a M/S signal, transform to stereo and collapse to mono, you basically ditch the S signal (you find the math googling).
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby MOF » Wed Nov 18, 2020 7:15 pm

The Mid and Sides system is used for recording with, typically, a cardioid mic’ facing the group (Mono) and a figure of eight mic’ above or below it (capsule centres aligned with each other) at 90 degrees (stereo information, which requires the M/S circuit to be heard correctly). This, when put through the M/S circuit, allows you to hear your recording in Mono and then progressively narrow to wide stereo as you fade up the S (figure of eight) channel.
The M/S circuit can also be used to make a conventional left/right recording into M/S, then by equalising and/or compressing either channel you can have greater control of how the stereo mix sounds without as many artefacts as doing the same to the L/R version.
In order to hear what’s really happening you’ll need to put another M/S plugin after the first one to convert back to L/R stereo.
There are recent articles in SOS that explain creative use of M/S processing.
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby armans » Wed Nov 18, 2020 8:11 pm

CS70 wrote:Panning controls left and right, and - while related - it's not the same as mid/sides.

Both L/R and M/S consists of two channels of audio, but while L/R is about left and right (and the pan controls affect that), M/S is about capturing a signal from the front and on the lateral sides of a source.

Think of having mic pointing at a singer and another pointing at the walls to the side of the singer (and since you want to point both walls you need a figure-8 microphone with two identical lobes, each pointing at one wall). You'll have two mono signal, one capturing the singer directly, one capturing the combination of the signal bouncing from the side walls.
It's a bit of a trick as a figure 8 mic is able to "see" two sides and mix them in a mono signal - so even in this case you'll have two mono signals, front and sides.

In M/S if you remove the S you're left only with the mic pointing at the singer, and if you remove the M you're left only with the "summed" figure 8.

You can always transform between the two and if you take a M/S signal, transform to stereo and collapse to mono, you basically ditch the S signal (you find the math googling).


Ar you saying the guitar in my OP was recorded with mid/side miking technique?
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Hugh Robjohns » Wed Nov 18, 2020 9:10 pm

armans wrote:... when I try to listen to the "mid" channel the guitar is still there, but ALSO, when I listen to the "sides" channel the guitar is also there.

Yes. Correct.

The reason becomes obvious if you consider the (simplified) maths of the mid-side matrix:

M = L+R ...and...
S = L-R ...or = L+(-R)

So for your guitar panned hard left you get M = L and S = L -- so the guitar appears in both the Mid and Sides channels, at equal volume!

The term 'Mid' is, perhaps misleading as it doesn't just carry sounds panned to the centre. It actually carries everything -- it is exactly the same as a mono summation -- but it emphasises sounds around the centre (slightly) relative to sounds at the edges.

Image

In contrast, the Sides channel carries everything except sounds at the exact centre, with emphasis of the wider panned sounds relative to those nearer the centre (and with opposite polarities between the two sides).

If the guitar was centre panned in the chorus then it should dissapear when the side channel is being auditioned

Correct.
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Hugh Robjohns » Wed Nov 18, 2020 9:17 pm

armans wrote:Ar you saying the guitar in my OP was recorded with mid/side miking technique?

Nope.

All this talk of Mid-side microphone arrays is true, but not relevant in this context.

Any stereo signal can be conveyed -- or auditioned -- in either the Left-Right or Mid-Sides formats, and even transposed between the two, back and forth, as often as you like without loss.

Mid-Sides microphone arrays have their uses, but they're not a prerequisite to auditioning the Mid and Sides components of a stereo signal.
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby CS70 » Wed Nov 18, 2020 10:11 pm

armans wrote:Ar you saying the guitar in my OP was recorded with mid/side miking technique?

As Hugh's said, no, not necessarily.

You also say that

in the chorus the guitar on the left comes in and the guitar can be heard both on left and right channels

With "comes in on the left" I assume you mean that now it's no longer hard panned but panned center? It suddenly moves (in the stereo mix)?
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Sam Inglis » Wed Nov 18, 2020 11:16 pm

armans wrote:If the guitar was centre panned in the chorus then it should dissapear when the side channel is being auditioned

This is true IF it's a single mono signal that is centre panned and not feeding any stereo effects.

armans wrote:if the guitar is double tracked or recorded in stereo, most of it would dissapear as the signals would be almost identical

This is not true at all of double-tracked guitar, and not necessarily true of a stereo recording of a single guitar. For instance some guitarists like to run one guitar through two amps with different sounds and effects on them. That can create a "stereo" guitar sound but there won't necessarily be much in common between the two sounds.

If you think about it... the simple fact that you are perceiving the guitar as being obviously stereo tells you that the signals aren't almost identical. If they were almost identical you wouldn't hear two guitars left and right, you'd hear a single guitar in the 'phantom centre'.
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby CS70 » Wed Nov 18, 2020 11:19 pm

Yeah I was thinking what armas is experiencing can simply be the result of duplicating the guitar for the chorus. If you take the guitar on three tracks, one panned central, two hard panned L and R, and reverse the polarity of one of these two (like a figure 8 mic does between the two sides of the capsule), you would get that effect: when both M and S are present, the two hard panned guitars on the L and R cancel each other, leaving only the one centered, but if you mute the mid channel, what is in the side are the two hard panned guitars in reverse polarity which, when making the difference, actually sum up.
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Hugh Robjohns » Wed Nov 18, 2020 11:33 pm

CS70 wrote:If you take the guitar on three tracks, one panned central, two hard panned L and R, and reverse the polarity of one of these two (like a figure 8 mic does between the two sides of the capsule), you would get that effect...

If your three tracks are of exactly the same source guitar track, this wont work!

The centrally panned version obviously appears equally in both the left and right channels. Your hard panned (+Sides) track then adds to the left channel, but the polarity-inverted (-Sides) track cancels the right channel... so you're left with just an extra loud guitar on the Left channel. Hmmmm... ;)

To make things work in the way you describe the Sides signal -- the opposite-polarity hard-panned left/right element -- must differ in a significant way from the Mid signal: it must have a degree of 'incoherence'. That's inherently what you get with an MS mic array simply because the mics are looking in different directions and so hear different things. In simple terms, the Mid mic hears mostly the source, the Side mic hears mostly the room....

Double-tracked guitar parts are usually different enough to be sufficiently incoherent for your idea to work, or delaying one track by a few milliseconds might be enough... but the rule is they cant be the same!
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby armans » Thu Nov 19, 2020 5:18 am

Hugh Robjohns wrote:
armans wrote:... when I try to listen to the "mid" channel the guitar is still there, but ALSO, when I listen to the "sides" channel the guitar is also there.

Yes. Correct.

The reason becomes obvious if you consider the (simplified) maths of the mid-side matrix:

M = L+R ...and...
S = L-R ...or = L+(-R)

So for your guitar panned hard left you get M = L and S = L -- so the guitar appears in both the Mid and Sides channels, at equal volume!

THanks for the reply. The math does make things simpler however there is a problem. The same guitar part is in both L & R channels. If the side channel is the difference between the two channels and the guitar parts are almost identical on both L & R channels in the chorus then they should effectively cancel each other out when the "side" channel is auditioned but this is NOT what is happening here. When I listen to the "side" channel during the chorus the acoustic guitar is perfectly audible with no cancellation at all.


I am going to uplaod a clip for you in case you want to hear for your self

https://gofile.io/d/7yfQ7W
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby armans » Thu Nov 19, 2020 5:25 am

CS70 wrote:Y

If you take the guitar on three tracks, one panned central, two hard panned L and R, and reverse the polarity of one of these two (like a figure 8 mic does between the two sides of the capsule), you would get that effect: when both M and S are present, the two hard panned guitars on the L and R cancel each other, leaving only the one centered, but if you mute the mid channel, what is in the side are the two hard panned guitars in reverse polarity which, when making the difference, actually sum up.

:clap: this is very interesting, :thumbup:

but why on earth would you do something like this? :o

would you be so kind as to listen to the clip I uploaded and see if you think this is what is happening?
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby armans » Thu Nov 19, 2020 9:35 am

Hugh Robjohns wrote:
CS70 wrote:The centrally panned version obviously appears equally in both the left and right channels. Your hard panned (+Sides) track then adds to the left channel, but the polarity-inverted (-Sides) track cancels the right channel... so you're left with just an extra loud guitar on the Left channel. Hmmmm... ;)

I tried this and there actually is a difference between a left panned guitar and using the three channel approach mentioned above. The resulting signal actually seems to be panned further than left if that makes sense. You can see it in a vectorscope. With a normal left panned signal the vectorscope is at 45 degrees but in this case it is at about 60 degress so it is further left than the left panned guitar. I don't know how or why that is possible but it is.
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Mike Stranks » Thu Nov 19, 2020 9:55 am

Do you know how this track was recorded/mixed? Do you have access to the original guitar track(s).

I've just had a very quick listen to the sample you've provided. I've only used my ears, but I suspect that the guitar part was recorded with one mic and that it has either been put through some sort of 'stereoising' process or it has been duplicated and then delayed by a few milliseconds with each track then panned left/right.

Just my initial impressions having listened to about 30 seconds...
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Re: What does it mean if an element in a mix is in the "side" AND "mid" channels

Postby Zukan » Thu Nov 19, 2020 10:12 am

Hugh explains it all eloquently in this article:
https://www.soundonsound.com/sound-advi ... ually-work

And if you fancy getting creative with M/S here is an article I wrote for this wonderful publication:
https://www.soundonsound.com/techniques ... techniques

TBH, producers have been working with M/S for eons and most of today's plugins come with M/S functionality, and I encourage all to explore this wonderful process.
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