Does Adobe Audtion decode or encode (whichever is correct terminology) a mid-side recording to stereo?

Are there any other programs or plugins that do?

If Audition can accomodate VST plugs, try this freeware decoder:
http://www.voxengo.com/downloads/?highlight=msed It works fine. Look for the highlighted plugin called "MSED".

But you might be able to build a decoder without plugins. I'm not familiar with Audition but try this:

Assuming that the cardoid/mid/mono element is on the left channel.

Make a total of 3 copies of your stereo recording on your timeline.

Track 1 - Left channel of the recording, pan center.
Track 2 - Right channel of the recording, pan left.
Track 3 - Right channel of the recording, invert phase and pan right.

If you have a way to group/lock the volumes of channels 2 & 3, do it. Stereo spread will be changeable by the relative volumes of Track 1 to Tracks 2&3.

If it's not sounding right, pan Track 2 right and Track 3 left. But if the wiring was right when recorded you won't need to do this.

This all represents the Mid-Side decoder formula:
Left = M+S
Right = M-S

It's really kind of magic...

I don't know anything about Audition... but you can also do the same thing Seth recommends by bussing the signals (instead of copying the tracks), which will be easier to manipulate and use fewer system resources if it's a concern. This also lets you monitor live in stereo rather than MS if you have your DAW along...

So: Assuming you have two mono tracks, "M" and "S" and aux busses 1 and 2:

Just send M panned center to your main outputs;
Send S to both bus 1 and bus 2
Invert bus 2
Send Bus 1 to Main Left and bus 2 to Main Right.

Now, you can just use the M fader to control volume and the S fader to control the width of the stereo image.

Again, I don't know if this all works in audition... but for anyone with ProTools or another systems that allows bussing, I think this has some advantages.

-Barry

P.S., I do a lot of MS recording, and I find it's always a good idea to record a test where you just walk from left to right in front of the mic, saying "Left... center... right" appropriately. This lets you very quickly make sure you've got everything properly set up in post.

Of course! I should have been able to figure that out, but I may never have. Thank you, gentlemen.

Or, go to Effects > Amplitude > Channel Mixer and choose the Preset Mid-Side o L-R in Adobe Audition.

/Roger