a Lady Gaga

b Birdy

c Lorde

d Katy Perry

a Daft Punk

b Cee Lo Green

c Bruno Mars

d Justin Timberlake

a Vanessa Hudgens

b Britney Spears

c Kesha

d Icona Pop

a Coldplay

b Radiohead

c Imagine Dragons

d Muse

a Martin Solveig

b Martin Garrix

c Robin Thicke

d LMFAO

a Jimmy Hendrix

b Bruno Mars

c John Newman

d Will I Am

a Christina Aguilera

b Carly Rae Jepsen

c Selena Gomez

d Anastacia