Britney's songs now aren't even that high. The highest she goes most of the time is a D5/E5 and she has shown herself capable of singing those notes live. Britney's problem has never been range but her poor breath support. She doesn't sing from her diaphragm, she sings from her throat/head and doesn't take enough breath so she always ends up sounding winded. It's not the songs themselves that are the problem it's her technique. She has certainly sang higher then a lot of the material she has been given the last eight or so years for her albums. Britney herself has even stated that her songs aren't that difficult to sing and that she has never been challenged vocally by any of her songs, and that was back in 99/00 when she had more demanding songs like Stronger, Overprotected, Lucky and Oops! to work with. Britney's material post Zone is a cake walk because it features virtually no belting. The only thing asked of her is a few low notes, an occasional high note in head voice and her general talk-singing range.
From Britney, I think some of you already answered it.
Wynter Gordon so far she has been doing great live.
September also but theres one live performance from Cry For You that was kinda messy tho
