From what I understand, Ozzy doubles each phrase as he sings it. In other words, he sings a line or a half a line, stops, then doubles it.

 
That may be because he can't remember much more than a line at a time...  
Seriously, Ozzy sounds pretty good for a guy who's put himself thru the ringer.
 
Double/triple tracking phrases is common place with background vocals.
That's how you get that nice stereo spread... where the parts take on an "ensemble" (rather than solo) character.
 
Key lines are also commonly doubled on the lead vocal, but it's usually tucked a bit under the main track.
 
All that said, (at the risk of repeating) I'd first make sure I'm getting a nice/full sound from the mic.
If that's not happening, the solution isn't in processing/treatment... but rather chosing a different mic.
Note that there are very affordable decent mic options today.  MCA-SP1 and the B3 are but two examples
 
 

Doubling is good "for effect" however, please note, you will get a "doubled sounding song" It's an effect which should be used sparingly IMO... If you double all of your stuff, it won't be good :-(

It's like that radio mic effect? It's cool in places? Or that Chere robot vox effect? It's coold "in places" And the doubled vox? "It's cool in places" However, if you try that "for a full vocal track... Get ready for dissapointment IMO... Your milage may vary...

Surpised nobody's mentioned the new VX64 vocal channel.

This comes with a tweakable doubler that IMO does a pretty good job at thickening vocals.

Here's a little ditty I put together yesterday to test out my new Purple MC77 hardware.

http://www.harmoniccycle....ckory%20Wind%2004a.mp3

It aint easy to sing a song you don't know while watching all those meters and trying to feel groovy.

I think feeling groovy is the most important.

1 take vocals. Royer 121 into John Hardy M1 into Purple MC77.

I rolled a whole bunch of bass off the vocals when I was done singing.

Everything else was one take as well... I think there's still a bit too much low freq energy in the mix.

I put a schmaltz of Pristine Space reverb over the master.

I've never heard doubling that didn't sort of sound like doubling. Maybe I have and didn't know it? :-) I've never done it myself and not known it... no matter how quiet I make the second track.

best regards,
mike

I've never heard doubling that didn't sort of sound like doubling. Maybe I have and didn't know it?

Bingo. Have you seen the documentary on the making of Dark Side of the Moon? I was surprised to find that just about every vocal (and guitar lead) was doubled. It's just done so expertly that you don't realize it.

Hey, speaking of documentaries....

Quote from American Songwriter Web site:

On Wednesday, November 25 at 10 p.m. Eastern, the History Channel will air “The Beatles On Record,” a new documentary on the beloved British band.
Featuring over 60 songs, with never-before-heard studio chatter, the doc “charts The Beatles’ extraordinary recording journey from Please Please Me to the epic Abbey Road LP and reveals how they developed as musicians, matured as songwriters and created an enduring body of work that pushed the boundaries of studio recording, changing the course of musical history and popular culture.”
End Quote...

Probably not too in depth considering I believe it to be a single one hour show, but I always enjoy looking at the gear and mic'ing techniques used in their studio sessions.

As far as thickening vocals goes, I've used a number or techniques, but luckily I usually work with vocalists that don't need much help. When I do doubling (unless I'm going for a specific effect) I usually ride the fader on the doubling track (with automation) to punch up the longer vowel sounds and leave the pick-up phrases alone. Doubling has a characteristic phase shift (dynamic comb filtering) sound that isn't always flattering. I also use a bit of compression, but not just any compressor. The UAD comps are pretty good, as are some of the Waves. (I use a leveling amp approach for ballads, or I might use something 1176-like with faster response on more aggressive tunes.) I'm sure there are others out there that are stellar as well. I also look for a subtle ambience patch in Perfect Space. (There are hundreds of impulse files avaialble on the web for free or a voluntary donation that can be used to expand your reverb pallet substantially). The kind of patch I look for is one that you really only notice when you disable it. On ballads, I sometimes add a send to a bus with a second (more obvious) reverb on it. I load an expander gate ahead of the reverb (set for expansion) with a slow attack and release. This puts a nice plate like effect on louder passages with longer tones, and can be quite subtle. Alternatively you can gain ride the reverb send from the track. When the full mix is up, I usually go back and tweak vocal levels, vocal eq, and reverb eq to get the most flattering sound. Use a good EQ for this (something like a Pultec clone).

bitflipper
Bingo. Have you seen the documentary on the making of Dark Side of the Moon? I was surprised to find that just about every vocal (and guitar lead) was doubled. It's just done so expertly that you don't realize it.

I didn't even know the documentary existed.  It's now sitting atop my netflix queue.  Thanks!  Can't wait to watch it.

bitflipper

I've never heard doubling that didn't sort of sound like doubling. Maybe I have and didn't know it?

Bingo. Have you seen the documentary on the making of Dark Side of the Moon? I was surprised to find that just about every vocal (and guitar lead) was doubled. It's just done so expertly that you don't realize it.

I don't know Bit, I think it's fairly obvious where they use doubling.

I doubt Claire Tory's solo got doubled but the ultra produced sound of the band's vocals are way different from the raw sound you get on something like Madcap laughs.

anyways...  :-)

A lot of great suggestions. Some are tried and true. I have gotten a lot of milage out of the VX64 plug-in. Probably one the best reasons to upgrade to 8.5. Antares makes a lot of plug-ins devoted to vocal processing and thickening. If you're just looking for a quick fix, I think all their products are available with a 15 day free eval. Fully functional. The DUO plug-in works great for this. Suprised no one used this to rant about the lack of varispeed in Sonar :-)

I have also seen, very randomly, singers who can actually sing in such a way that they have a natural thickness to their voice. It's a sort of growl or throat distortion that seems to create a doubling effect. When you encounter one of these singers, it's pure bliss to record them.