In Graham Cochrane's Rethink Mixing Tutorial (http://therecordingrevolution.com/2011/10/17/welcome-to-rethink-mixing/) one thing which he said that really struck me was to mix in mono..of course you pan instruments and voices in the stereo spectrum, but always make final reverb, eq, level, and compression decisions while listening to your mix in mono. He said that if your mix sounds great in mono, it will sound even better in stereo.

In his tutorial, he inserts a stereo-to-mono-to stereo plug-in in the master bus in PT which he toggles on and off to check his mono mix.

In Sonar X1, I found that toggling on or off the stereo/mono mode icon doesn't seem to be the right way to check. I may have a relative good sounding stereo mix, but when I switch the master bus to mono...the mix sounds really bad....(e.g., reverb sounds too diffused, instruments panned left / right get lost in mono, etc., etc.)

My question to you guys is....how do you quickly A/B your mixes in Sonar between stereo/mono?  Is there a free plug-in out there that I can insert into my master bus that will do this?

Thanks.

Channel Tools?

there are several things to consider... all the tracks need to be in mono mode, then you need to check all your vsts to make sure force stereo operation is unchecked then from the standpoint of dimension or any other vst that uses .sfz files you need to check the sfz files to see if for width parameters (specification is here: http://www.cakewalk.com/DevXchange/article.aspx?aid=108). For Extreme control, split synth tracks with an audio channel for the left side and right side, orbounce everything down split mono and pull them into a separate mix/master project. The export audio options would look like this...

https://skydrive.live.com...d=5DBE71A770FCC390!302

I use this http://www.kellyindustries.com/stereo_tools.html

I have the mono button permanently engaged then just toggle the plug-in on and off to check. I have it set as an FX chain in the Pro Channel, on the master bus.
 
 
EDIT:
 
You can do the same with Cakes own Channel Tools, have it set like this for proper mono summing...
 

Yes, it even has a preset already made for you

There may also be some advantage to only listening to one of your monitors when mixing in Mono - grab a copy of Mike Seniors "Mixing Secrets for the Small Studio"

He explains all of this in great detail (and it's a superb book)

Thanks guys, completely forgot about the Channel Tools plug-in!

Found this too, though....http://music.service-1.de/html/m-st.html

one thing which he said that really struck me was to mix in mono..of course you pan instruments and voices in the stereo spectrum, but always make final reverb, eq, level, and compression decisions while listening to your mix in mono.

Viscant, mix in stereo and check your mixes in mono. Don't mix in mono. The same analogy goes for headphones. you check your mixes with headphones, but you do not mix with them.
 
To check your mixes in mono, you can change the interleave on your master bus (keep in mind the pan laws and how they effect your mono signal) and the channel tool as many said can be used. Now when ever you change a stereo signal to a mono signal, your volume will increase (pan laws) because your combining 2 channels into one channel.
 
CJ

Boxes like the Big Knob, C-Control, etc. etc. have mono buttons. Also lets you check other stuff in mono, too, like anything else from your computer, an external CD player, etc. FWIW.