vocal effects?

Hi. Which version of SONAR do you have? The later ones include V-Vocal (up til X3) and Melodyne (X3 and forwards), which allows you to do this pitch shifting, and is specially made for vocals. But I would try (if you have access to one of those) to sing as close as you can to 3rd or 5th, and use pitch correction after that to achieve more of a backing vocal feel. There are probably free ones you could try if you do not have neither. Others might have other ideas.
All the best.
Edit: To my knowledge, pitch correction does what the title says, and corrects / alters pitch. Some are better than others, and Melodyne seems to be up there with the best (if not the best).

Hi Ken and Led
Thanks for the great tips.  I have X3 studio.  It's the very basic version of Sonar.  I'll look into the Melodyne.  I've only heard of it but no idea if its installed or what it does.  
 
Hey Led good idea.  I'll try sing along as you say with a synth or even a temp guitar riff starting on one of those notes.   I might mute the main vocal when doing this.  My own vocal is forcing me to sing the exact same pitch.
I take your point guys and I do agree with you.  If you can sing the vocal naturally it would be better. 
Thanks guys  :)
Xave

I have a friend that has a good voice but just can't sing harmony.  He always slips back into the lead melody after a line or two.  So, I had him learn the phrasing of the lead vocal to a T, then I muted the lead vocal and had him sing the harmony part as if it was the lead vocal.  He could do that just fine, and when I added the lead vocal back in, the two parts were in sync and in perfect harmony.  Anyone can do this if they have good timing and the song lends itself to this procedure.

Taxi telling you to add harmonies seems a little odd.  I'd think you'd only add harmonies where harmonies were required by the song.  Duh. 
 
As far as vocals, nearly every vocal you hear has been doubled (sang the same notes twice and dropped the double back in the mix).  Sometimes I will even double the lead vocal twice, and pan them hard L and R, and back them down in the mix.
 
In the last song I did ("Brain Grinder" youtube link below) I also did the +/- 3, 6, 9, 12 detune vocal fattening trick by cloning the lead vocal 8 times and pitch shifting.  Although my Aux-fat track it is pretty far back in the mix, it was noticeable when I turned it off.  So I think from now on I am going to add that to my standard bag of tricks.
 
When it comes to harmony, other than hitting the right notes scale-wise, I always double each part and do the LR pan trick.  For 5 part harmony (I'm a singer - my granny sang with the Met) that winds up being 10 tracks, and a lot of sweat and body odor in the vocal booth.

I mostly follow what many posters have suggested...I write all the melody and harmony parts to midi tracks - one track per part - and then play the specific part I am recording voice for along when I sing. I record the main melody line first, then tweak it with Melodyne and otherwise get it in good shape, then mute the midi lead vocal, but play the sung lead vocal along with midi harmony_part_1 while I sing harmony_part_1...Then Melodyne and fix harmony_part_1 and mute midi harmony_part_1 and move onto harmony_part_2 etc.etc.etc...
 
If I am singing high harmony parts, sometimes I will not try to sing the highest notes that are up out of my range, but rather repeat a lower note and then push it up using Melodyne.
 
I have one song that the entire harmony part is a simple raising of (generally) a third above the melody line - done using melodyne. I did this because I wanted to get it done quickly to see what it would sound like...and it actually did not turn out all that bad. Here it is if you want to listen: "Open-Eyed Girl".
 
Some things to remember if modifying the melody track into a harmony track:
>You will need to do a lot of fixing of formants and other aspects of the modified track.
>You should offset pitch and timing of the modified track.
>You need to know how to write a harmony line. As stated by other posters, it is not a simple matter of moving everything up a third, fifth or any given interval. It needs to fit withing the harmonic structure of the song.
>The bigger the change from the original note, the stranger the new note will sound.
>This works best on harmony parts intended to be in the background, not duet singing.

There's fantastic advice here. I'd only add that any effort you can put in to practicing nailing a harmony while the lead vocal is singing, then eventually learning to make up harmonies on the fly will pay off for you. There are tons of instruction videos on the net about this fascinating subject and one is out there somewhere that will work for you. It takes time but it can be done and is so worth the trouble.  It's just practice, right?

I don't sing myself but I often arrange vocal harmonies for others to sing. If the vocalist is not good at harmonising against an existing lead vocal, I sometimes create a guide vocal for the harmony using a copy of the existing LV by pitch-shifting the notes using either V-Vocal or Melodyne. Although it always sound artificial, it's usually adequate as a guide vocal. It works better still if, instead of using the existing LV for this, I base it on a suitable alternative LV take (or clips from different takes). This way, although the harmony itself still sounds artificial, it will sound a bit more convincing alongside the LV.

Bristol_Jonesey
 
It's a real chore to have to fix the timing of words/syllables, especially on sibilant sounds like s's or t's - it sounds really amateurish to have the end of a word ending in s-s-s-s-s-s
 
Another way to overcome this particular problem is to only sing sibilant endings on your main vocal, don't sing them in the harmony overdubs, but watch you don't crack up with laughter when doing this!
 

Actually, I find myself sometimes doing THE EXACT OPPOSITE! If I have a tune where I feel the terminal consonant for a word was weak or missing....Usually a "t", "st" or "d" sound. I then create a special audio track in Sonar and sing along with the lead vocal, but ONLY sing the missing consonant! Played alone, this track sounds really strange, but when split up, mixed in and nudged back and forth with the lead vocal, can add some missing definition to the lyrics.