Christina Aguilera's gutsy persona and gravity-defying range have fired up the engines of plenty of singers. Charli XCX's giddy party track “SuperLove” echoes Aguilera's Lotus-era plunge into bubbly Europop; Little Mix's message of solidarity “Wings” intensifies the inspiration found in “Beautiful”; and Kelly Clarkson's “Miss Independent” shows an Xtina-esque facility for blending vocal acrobatics with hip-shaking romanticism.