I've mentioned this many times in many posts. Doubling, or re-recording a track, will do things to 'thicken' its sound in a way that no effect can duplicate. Automatic double tracking (ADT) and subtle use of chorus approach, but never quite reach it.

I knew this, but had it brought home in the early 80s when I cut a guitar track using a solid-body Kalamazoo electric guitar with one pickup and a Masonite (chipboard) body. I only laid down two tracks with cheap spring reverb laid over the two. Listeners thought I was using compression and stereo chorus, which was then an expensive and uncommon effect. Nope, just a simple rhythm part played twice.

Singers Gilbert O'Sullivan ("Alone Again, Naturally") and Michael Franks have made it a trademark of their recorded sound. To the trained listener it's obvious; to others their voices have a sort of 'density' which set them apart for reasons the listener cannot explain.

Less obvious but far more extreme, Art Garfunkel, Sting, and many others have been known to lay down dozens of unison tracks. (They're good, of course, but nobody's voice sounds that good by itself.) Crosby, Stills and Nash each used to record each other's vocal parts in the studio as well as doubling their own, resulting in yet another degree of sparkle.

The process of tracking has another effect. As you try to duplicate earlier takes, you will hear embellishments and vocal 'tics' of which you may have been unaware. If they were not absolutely intentional and you can't repeat them every time, it will force you to simplify the part until you can repeat it note--and embellishment--for note. You will still never exactly hit the same pitch or match your phrasing to the millisecond, which is what gives it that density.

Once while engineering a jingle, the talent was a 12-year-old performer. The producer thought the first take was acceptable but a little thin. I suggested doubling, but went a step further, as I was uncertain of the child's experience. I had the singer omit the final consonant of each word in the two succeeding takes, as without the most careful phrasing these stand out garishly. The kid nailed it and the producer was very happy. I was secretly pleased myself as it came out better than even I expected. (And the young singer probably could have matched himself without that trick; he was good.)

Once you've gone to all that trouble, and have however many succesful takes you want, you can start
playing tricks. Keep the doubled tracks back in the mix. Pan them slightly (or not). Use "crossverb"--delay panned to the side opposite the voice or instrument. Be creative and use different effects. Peter Gabriel commonly uses a pitch shifter for an octave up and down. But unless you want it to stand out as an effect, keep all of this very subtle.

All the performances above were done on an analog four-track recorder in mono. Most of us have virtually unlimited tracks. The only cost is the time it takes to do the additional takes. Why not give it a try?

"My primary musical instrument is the personal computer."