Harvey Gerst just might be on the right track!
Ok Harv. You are definitely in the direct area. Since you ARE talking about a TECHNIQUE used in the actual recording process; that many "local" artists, producers, and even engineers that MAKE rap locally, obviously dont know about.
I am VERY aware of that technique. The one you spoke on about the "posse" track. Or the backround vocals. We also call it the ad lib track. There are usually a minimum of three, to as many as necessary, of these tracks taken on many, if not all known rap songs today.
One of these "ad lib" tracks; would be the artist repeating in unison, only the ENDS of sentences, or some specific words or phrases WITHIN the sentences, of each line. That specific take is for energy and to evoke a mood through enunciation. To make you take a sort of feeling or relation to whats being said, by "doubling" certain situations in your lyrics, for a stress factor. i.e
"like your right hand to God, LORDSIRE, THE TRUTH!"
FEEL that "LordSire". HEAR that "The Truth". STRESS the words that i want to stand out. Thats how you evoke emotion in your verses.
The TRUE ad lib track, is just that....its that "surreal", or even sometimes boisterous (see Lil' Jon or Young Jeezy) set of "yeahs" and "uh-huh's"; or even for a THIRD time, with the same ends lf lines or stresspoints as before. (I believe those are the triple tracks you speak of). For all that would like to know the "formula", or some basic steps to take, to what's being done as a regular practice, for laying or recording your vocals in todays hip-hop industry; there it is. Basic. Refer someone to this thread if they happen to ask. Now mixing those well, into the mix, is a BITCH! (Not to toot my own horn) But i have NO PROBLEMZ with those; at all.
Now....................If you DELETE, or MUTE ALL those "backround tracks", ad-lib tracks, and/or "posse" tracks: And LEAVE the main lead vocal track. On that track ALONE; there is a distinct "doubled" track that sits under the lead but is simultaneously, or just "hairs" off, THAT effect, in MOST professional situations, is a replicated version of that exact lead vocal. THATS the effect ive been talking about.
Now my ears can dignify that it is NOT a seperate vocal track taken. But, with tryng effects like chorus, delay, and echo, i dont get it.