Nicole KidmanKeith Urban has apparently been writing a ballad for Nicole Kidman - and Star magazine in the US is claiming Nicole wants it to remain secret as it’s their “wedding song and no one else’s.”

“He’s been trying to describe how he feels about her in song for months now,” a close source revealed to the magazine.

“He has struggled with it for weeks now, but has finally found his groove.”

She apparently cried the first time he played it to her: “she told me it was the most emotional experience she has ever had,” the source added.