` That 's because , most likely , Spears uses Sia 's track as an in-monitor guide when she sings . Billboard says you can hears Spears singing under vocals . Track is reportedly of singer / songwriter vocals . Billboard backtracked on saying Spears sings live .
Billboard says you can hears Spears singing under vocals . Track is reportedly of singer / songwriter vocals . Billboard backtracked on saying Spears sings live .