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The Torchwood star's latest self-titled album peaked at number 11 in the UK album chart earlier this year.
He told What's On TV: "My dream would be to sing with Celine Dion. I would wet myself if I were on stage singing and she walked on behind me.
"My other dream was to sing with Barry Manilow, and it came true last year at Proms in the Park in front of 45,000 people. It was awesome."
The 43-year-old, who appeared in the last season of Desperate Housewives, recently admitted that he wants a role in Glee.
> Barrowman: 'I turned down Eurovision
