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"The set list for Britney&amp;#039;s &amp;quot;Piece of Me&amp;quot; Vegas showcase includes her recent single &amp;quot;Perfume,&amp;quot; a track written by Sia Furler. (Sia basically writes everything you love to sing along to these days, she&amp;#039;s that good.) And Sia clearly recorded a demo version of the song to present, for consideration, to Britney&amp;#039;s team \u2014 because her vocals played during one of Britney&amp;#039;s recent shows. Which is awkward, and rather confusing:         V\u00EDdeo de Perfume pela passarela! #PieceOfMe #PlanetHollywood #TheAxis A video posted by Britney Spears Brasil (@britneysite) on Aug 16, 2014 at 9:58pm PDT     It&amp;#039;s possible that Britney can just do an awesome job of singing like Sia; it&amp;#039;s also possible (though certainly most unlikely) that Britney has in fact always been a puppet, ventriloquism-style, and Sia is behind a decades-long piece of postmodern performance art. But the best explanation, via Billboard, is that Britney uses Sia&amp;#039;s vocals as &amp;quot;an in-monitor guide when she sings,&amp;quot; presumably via an earpiece feed. On this unfortunate occasion, the track meant only for Britney&amp;#039;s ears ended up in the &amp;quot;house mix&amp;quot; for everyone to hear. And this is why, in the Instagram clip, you can also make out Britney&amp;#039;s reedy vocals in part \u2014 it&amp;#039;s not that she&amp;#039;s totally lip-syncing, just that there&amp;#039;s a backing track to help out when she&amp;#039;s dancing and all. (Britney&amp;#039;s manager Larry Rudolph acknowledged that backing music would be in place to help her out in a previous Billboard interview.) Follow Alex on  Twitter. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.cosmopolitan.com/entertainment/celebs/news/a30176/britney-spears-sia-perfume-lipsync-what-on-earth/>