I've used Soundtoys' Microshift and Waves' MondoMod to try to get background vocals to widen.    I know they're a stereo chorus, but for me they don't sound natural.    There's too much phase.
 
Here is a video of Microshift on background vocals  (around 1:04).   On my speakers, it sounds fine.   
 
https://www.youtube.com/watch?v=WmtmNQPreQA
 
But it sounds nothing like that when I use it.
 
So what do you guys use to widen vocals?
 
Thanks!
Greg

I copy the vocal track. Then I do some hard panning (LR). Then I am using the EQ in a strange, but helpful way:
On the first track I focus to one frequency, like 400hz and push that by 3db (with a low q-factor). Then I focus to another frequency, like 2khz and lower them by 3db.
On the second track I do it in reverse: Lowering the lower frequency and pushing the second one.
As a result, the vocal track sounds much widener without having artificial stuff going on. Just try to find the right frequencies depending on the source material... 

Do you do this just for background vocals, or with the lead vocal as well?
 
Thanks!
Greg

WAVES S-1 PLUG
 
http://www.sweetwater.com/store/detail/S1StereoPlug?adpos=1t1&creative=83049426001&device=c&matchtype=b&network=g&gclid=CObdnem3jskCFZWDaQodehENkQ
 
 

Hello, I would have to agree with all the advice so far.  However, I am reminded of a post by that "Lord Tim" gentleman when he was helping Sir Beepster sort out some issues. 
 
He said, "sometimes you have to do it the slow and tedious way."  And then he mentioned that sometimes he does 150 plus vocal tracks.
 
I believe that the truth of the matter lies somewhere in the middle; the judicious use of software and the layering of different takes one on top of the other.
 
I hope you can find your sound.
 
Jesse

Yeah, cloning doesn't give you that huge width that layer upon layer does, unfortunately. Tedious as hell but man it works! The EQ trick and a bit of sliding around does work to a degree but it tends to collapse a bit when you sum to mono.

Danny Danzi also mentioned Clone Ensemble and that's great alternative if you need a quick fix. So long as you have at least 3 or 4 unique tracks (either the same or harmonies), that can really add a lot of size to everything.

There are so many tricks...
 
1. Double Mic using different mics and panned slightly differently. This also gives the performer some control because they can twist their head to get a cool stereo effect.
2. Track it repeatedly. Nothing like real singers singing along. This can be tightened with vocal sync.
3. Dup the track and offset in time/pitch/eq or any other way. Differing delays maybe. I find this to be a long run for a short slide.
4. Get weird. Reverse the vocal track and apply delay then Reverse it again. Now you have pre-delay. haha fun!!
 
Often backup vocals get longer reverb tails than lead vocals.
 
This one was tracked with two vocal mics...
http://stabilitynetwork.blob.core.windows.net/g-tunes/20150723_Tony_21_BeautifulLoser.mp3
 
 

are we talking about 'widening'.........
 
or stacking?
 

Toneboosters used to have a free plugin called TB OmniSone (32-bit). They don't support it anymore but there are places like this where you can still download it from:
 
It's my favourite plugin to make mono tracks wide for free.
 
I'm not allowed to post links but the website was 'don't crack'

batsbrew
are we talking about 'widening'.........
 
or stacking?
 

Both..the more original vocal tracks you have, the easier it is to get them spread out wider. Did a song ('Anchor Up Captain', see link in sig) recently where Tim (the singer) did 18 parts for the backing vocals, once we got going it didn't really take that long. Spread 'em out and used varying reverb busses, sounded good.