I am talking about mostly higher frequencies. I have noticed that a lot of professional music seems to sound like it has a ton of stereo width. But when I look at it in my daw with a stereo imager there really is not that much.
I dunno, I don't really experiment with stereo imaging, stuff I want wide I just put wide from step 1. After that I don't really check if it would sound better mono.
That being said, a little disclaimer, I do play around with panning, Just to clarify.
Not sure if this is any help for your problem though
the trick is to put the right things in stereo to create the impression of width, but things like your kick/snare, lead and vocals, are all straight down the middle
what you want is to add a little bit of (for eg) vocal reverb on the edges, a little bit of percussion top end on the edges, and FX etc in full stereo
bare in mind that Contrast plays an important role when it comes to your perception of a sound, if you have lots of stuff going on in stereo, you don't get as much impact as if you have lots of stuff in mono and just a few key elements in stereo
Try putting the higher frequencies of your bass with more stereo image than the lower ones, for example, when you separate your basses in three different bands for processing. Same applies to snare, you could give it's higher frequencies come stereo imaging as well.
word up to Dark Lizardo, tots agree. stereo width is really about giving the illusion of space. percussion, particularly the kick n snare, tend to sound best dead center, with the more harmonic/melodic elements of a track (e.g the synth pads, or guitar or w/e) sounding 'best' with wider imaging. like, panned pretty far out. Chorus effect is a good way to do stereo imaging. or if you work in logic there is a tight plug-in for stereo imaging
I think its best to learn good panning, before playing around with stereo imagers myself, they can be very useful, but until you get a good grasp of the stereo soundscape, you can just as easily mangle the mix
if you program your own drums, simply pushing hihats, rides, tambs, etc off by ~5% in each direction left/right, while your kick and snare are in the middle, can really bring allot of life to drums - and then have the occasional hit further out, ~20% or so, strategically placed in the phrase, can open the mix up beautifully
A lot of what I'd say has already been said really.
I use more stereo than I used to but a lot of my early stuff was solely in mono and it still sounded fine, that was just the vibe I was making at the time. Jungle or anything that's quite rugged in production will still sound good in mono.
About the only things that haven't been mentioned are using reverb with a wide setting or using ping pong delay. That can work well to fill out space.
Having strong mono signal is the key to strong mixes. Your sound and its key elements must sound strong in mono.
I do most of my mixing in mono in such way that i insert a "monoizer" plugin on my master (and often tracks, too), then make sure all vital elements (drums, bass, pads etc) can be heard as loud as i want. Then I make it stereo again and apply width as desired.