ayu's earphone!

[Thulanks]

I guess no one really answered the question 'bout the backing vocals, well first the music is recorded (this way actually: drums, bass, guitar ,piano, FX, ) then the lead vocals are recorded (once the music's recorded it's easier to follow the tune listening to the instruments, that's what u hear in the studio's headphones) and then the backing vocals can be either recorded by the singer (or other singers) or made in the computer during the mix. U basically sing the chorus but at a lower octave (i dunno if u call it like that in english) or at a higher one. But u gotta be kinda well trained to do this.
In live shows u can't listen a thing of what u'r singin (in fact u don't even listen the people) the stage is very quiet (4 me, it feels like the studio, actually) so in headphones u listen to yourself, the music, and any comments that the guy in the console (sound engineer) wants to tell u (like 'hold on for the next song, the pedals of the lead guitar ain't workin').
And about Ashlee Simpson (who I don't know but I know someone who does know her) she listens herself (on the earphones) and also a vocal track 'cos she has no muscular memory (the one that makes u memorize the position of diaphragm (i dunno if it's said that way) and mouth to make a certain tune) for tones and can't find 'em just listening to the music.
I hope i've helped u, and sorry if i wrote sumthin' really long!!