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A demo version of Britney Spears' song Alien leaked online this week and the pop star received a load of criticism for her unedited vocals. The track sounds significantly different than the version that appears on her 2013 album Britney Jean.

Quickly after the song leaked, producer William Orbit took to social media to defend Spears and said the leaked version was simply a warm up.

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"Warming up is essential if you're a pro, as it is with a runner doing stretches, and it takes a while to do properly. I've heard all manner of sounds emitted during warmups. The point is that it is not supposed to be shared with millions of listeners," he wrote on Facebook on July 7.

"A generous singer will put something down the mic to help the engineer get their systems warmed up and at the right level, maybe whilst having a cup of herb tea and checking through lyrics before the session really kicks off. It's not expected to be a 'take'."

The producer, who has worked with the biggest names in the industry, including Madonna, went on to say that the leaked version can't take away from Spears. "She is magnificent! And that's that," he said.

Listen to the leaked version below:

Tags: Britney Spears