I really don't know what you are trying to accomplish. Are you trying do like Buddy Holly did with "Words of Love"? If you have a good condenser mic with spit shield and add little reverb, you should be able to do a real good vocal.

I have recorded vocals on three separate tracks with me harmonizing with myself. It sounds like 3 different people. It sounds like something from "Oh, Brother Where Areth Thou". But you are wanting to "Overdub" to make it sound like one person with a better voice?

I'm afraid I can't help, but I thank you for stirring my curiousity.