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The Girls Aloud singer has worked with producer Paul "Groucho" Smykle on a new club track, reports The Mirror.
A source said: "The pair met up at Kensington Park Studios last week and got stuck into working on a new sound for her.
"She really wants to make people sit up and take notice, with a single that would never have been expected from her.
"Sarah realises it's time to try something different, so she's having fun experimenting."
Harding was rumoured to have been writing a collection of "heartfelt" songs about her rehab and relationship issues in January.
She has previously released solo material as part of the soundtracks for St Trinian's 2 and Wild Child.
Girls Aloud are reuniting for a new tour in 2013 to mark their tenth anniversary and are also tipped to record a new album together.
Listen to Sarah Harding's 'Too Bad' from St Trinian's 2 below:
