Your thoughts, please (great or small). 
 
I've struggled with mixes, especially narrative ones that I've written, where one lead vocalist rarely can fulfill the song, so to speak.  
 
So many times I duet or sing parts with others lead singers and choirs, often arbitrarily ... to provoke inspired performances and/or alleviate egotism, boredom, loneliness, tiredness, single-mindedness, or whatever.  Myself, I'm not a one-man-band, knowing my frailties, etc.  So don't let me get dogmatic about multiple lead singers making a song great.  Its just that I myself prefer multi-vocs oftentimes.  
 
You and I can tell when a singer gets inspired, peters-out, and then fakes it (waiting for the muse ...haahahaha).
 
Things do get funky.  It's been a bit hilarious having multiple singers to sing with.  Everyone has his/her moment in real 'performance-time'.
 
IOWs: When I sing, I notice that I often peter-out after 'that' inspired section ... hoping for the muse to regain life, etc.  Those are times when I hope my fellow singer(s) can 'pick it up'.  
 
There seem many quirky reasons I have problems with just 'one' lead vocalist in my mixes, but I'll spare you.
 
Again, please share or indoctrinate your thoughts on single vs. multiple lead vocals in pop songs, your mixes, performances, or such.
 
Utmost thanks in advance!
 
(P.S.: Apologies if I don't respond for a while due to day-job, etc.)

You always bring great questions to the table, Philip. In my opinion, there is nothing wrong with multi-vocal performances as long as the vocalists are singing material that fits them. See, one of the things that people fail to realize is, when you sing a song, you can sometimes just be going through the motions. To LIVE a song through the vocal line is where it's at and what makes a vocal come to life in my opinion.
 
You can have the best classical singer around singing on your stuff. If they are just going through the motions or singing what is there while not putting themselves into the mix, I think that 7 times out of 10 you can get a very stagnant performance.
 
When I sing on client material, I always try to stick to the melody they give me as often as possible. However, what happens if the melody they provide isn't right for my voice? The end result will usually be something that is not felt.....it would be me going through the motions for either a pay check or to just please someone. Fortunately (or unfortunately depending on whether or not someone likes working with me LOL) if I can't feel or live the vocal part to the best of my ability, I will try my best to come up with something as good or better that is also more of a fit for my voice. If I fail there, I will pass and not sing at all over just throwing something down.
 
Thankfully, it's been rare that I haven't been able to provide something as good or better than what I've been given when it comes to accentuating my own voice on a piece of music. :) I know my limitations as well as where I feel I can make something come to life. To me this is what makes a vocal have that little extra something. It goes beyond how good the voice is in my opinion.
 
It's a melody that fits....it's a vocal part that is effortless, yet can have an artistic personality. That said, I come from the school of having a pleasing timbre as well as singing and being in key. I guess it depends on what a person considers "a vocalist". Me personally, I'm partial to "singers" that can actually sing more than people that cannot sing that consider themselves "unique". Having several of these types of individuals on one song can be pure bliss really.
 
To answer your question though, I think multi-vocal songs add color and personality. That's one of the things I've always liked about your material. Between yourself, the choir of children you assemble and all your guest singers, each "Philip song" gives me something cool to look forward to.
 
That said I also like dedicated singers too. It all depends on what you have to work with really. Singing sure isn't easy and if you write a song that is great that may be challenging you vocally, it's cool when you can get a few different people to sing on the song. Other times a single vocal will suffice.
 
In your case I think the multi-vocal approach has added to your particular style. It makes your entire line-up of musicians stars of the show to me. :) The drummer in my original band plays in a cover band on the side. Every 3 songs or so they get up and change instruments. It's actually really cool to see and hear because it keeps the songs fresh and you don't hear the same things going on with every song. Different lead vocals, different guitar, bass and drumming styles, it's like a new band takes the stage every few songs.
 
I sort of get that same vibe with your stuff. You may use a programmed drum beat in one song, have a full real drum kit on the next....4 different singers, guitars by 2 different guys, synths by you, or someone else.....this keeps things pretty fresh and allows everyone to put a piece of themselves into the material in all aspects in my opinion. :)
 
One of the problems that sometimes can come out of stuff like this is when you get too many talented people on one recording. Each person can sometimes try to outdo the other. Sometimes this works for you, other times it can work against you. The best people are the ones that play for the song, not for themselves. HOWEVER....I feel that before you can give a great performance you must have a comfort zone. This to me is one of the most important elements I can have when I work on a project. The worst situations I've been a part of were the projects where I didn't have a say or I've felt like a puppet on a string. The more uncomfortable a person is, the more you'll most likely get that "fake" artifact you mentioned. Then again, sometimes we need someone to paint the picture we've scripted. Some are great at doing what gets asked of them, some are not. Part of the challenge will always be choosing the right painters for the picture. But that part usually makes things fun and sometimes, VERY different. :)
 
-Danny

i double take a LOT of my own vocals.
 
i like it.
 
i can do it.
 
it just depends....
 
 
here is a great example of double-tracked vocals, done as well as it gets......
 
http://youtu.be/aNHFtJsbcYc
 
 

ANOTHER STELLAR EXAMPLE
 
https://www.youtube.com/watch?v=9qcz5KATX6c
 

Thanks Danny and Bats,
 
Double tracks to solidify that endearing vibe of the solo-vocal is pretty standard now I believe: So many ways to multi-track for that sumptuous vocal! :):):) But that seems almost a 'straw-man' diversion of this thread (Bats).  
 
The thread-issue (as Danny addressed) for me is 'enabling other singers to parade in the song'. Who, when, and why?  To make it meaningful.
 
Caleb (my son) stated: "A listener may become endeared to particular singer's vibe(s) as songs play ... 'expecting' the vibe to recur."  Something may get lost in a song if a singer is suddenly 'shut out' by another singer.
 
- I'm pondering perhaps up to 3-4 different singers (trio or quartet) is probably a maximum number for 'my short songs'.
- Up to 3 intertwining vocal harmonies and counterpoints (trio)
- Duets for love songs or spiritual songs ... plus a choir or 2.
- ELO (Jeff Lynne) used 2 choirs at times, an operatic and his own band's singers (in the 70s) ... but did so judiciously.
 
Thanks everyone for your thoughts!

So many ways to multi-track for that sumptuous vocal!

 
 
i have to disagree with this statement....
 
FOR ME,
there is only one way to properly do multitracked lead vox,
and that is to sing it twice.
 
no computer tricks, no fx, just honest performances that are dialed in.
it's dirt simple, and really hard.
and worth it.
 
but, there is nothing that demands it, 
except to serve the need of the song.

i'd say, QUEEN set the standard for what can be done with multitracked vocals.
 
here's the single best example i can find of their work that shows this talent:
 
 
http://youtu.be/oO2SIa1TEDQ
 

for an example of TWO stellar lead vocalists sharing duties off and on throughout songs, and across songs,
listen to any Eagles tune (glenn frey, don Henley)

You might find this article interesting on gauging when to anticipate that "inspired" vocal.
 
Much is a matter of personal preference and the material. My goal is to achieve a solid performance by myself in a single pass. I think a single vocal has more impact that a double-tracked one but double-tracking can be useful.
 
However, I recently tried the kind of thing you suggested with a guest vocalist where we would "trade off" phrases the way two instrumentalists would. It sounded like it would work in my head, but given the personal nature of the lyrics, there was a disconnect when going back and forth between the vocals. I ended up using his harmony parts to complement my solo vocal, which worked fine.
 
So at least in this example, ultimately it was the lyrics, not the music, that dictated whether multiple lead singers would work or not.

Ah, multi-vocs, multi-tracks, and now multi-TAKES :):):)  Please forgive my errors below...
 
Thanks, Bats, you certainly have indoctrinated me (I love your words: "Its dirt simple and really hard") ... or you/I can certainly start another excellent thread to try to validate and/or 'quantify' the utmost excellence of double-tracked vocals (a vital issue for all of us).  (Mercury's samples certainly are often DOMINATING (putting everyone else into oblivion), imho, if sumptuous, too; there were a lot of excellent (but pretentious) multi-vocs dancing and blending in your (Queen) URL, too, that I loved and hated (like so many of Mercury's show-offs (capturing the moment))).  (Off topic: I'm curious how Frey and Henley would have benefited from Mercury's double-track excellence)
 
Bats, I'll be listening to Eagles more closely for their duets.  Honestly, you've enlightened me that they were duet-ing.  I guess I can't tell when Heart is duet-ing either.  Sometimes multi-vocals just aren't contrasty enough to be remembered.
 
Craig: You also appreciate the issues I've run in to.  Dreaming it and creating it are different.  Your blog helps with my "takes" issues as well (your graph-peaks seem a lot like mine).  I like your quantifications of "gut singing" vs. "rock steady" in your blog, too.  You stated there: "I wait until I have enough takes in the can that I know it's possible to put together a good part."  :):):):):)  Well said (for me).
 
But I agree with Bats about double-tracking excellence ... surely WHERE instruments are wanting or the vox needs thickening.  Single-tracking is oft boring to me ... how to accrete a vox-sample into the singing aspect.  
 
When my vox is raspy, I prefer single tracks (I almost said "takes").  
 
Julianna (Julibee) doesn't seem to require double-tracks (to my ears); her mic-pre and vox are 'enough'.  Yoyo (often doubles (high and low samples)), Danny (oft doubles and triples (high,mid,low), and Rick (always doubles (mid,mid) ), yes.  Children oft do well with single tracks, due to simplistic vibes.
 
"Its dirt simple and really hard" :):):)
 
I'm pondering that Bats invokes singing on key/timing with utmost inspiration TWICE ...  simple procedure ... hard to perform ... in Bats' Classic Rock scenarios (which I emulate).  (... which gets into Craig's inspired "multiple takes" issues (which Craig addressed wonderfully to me))  
 
(... not to be confused with multi-vocs and multi-tracks)