Singer Cyndi Lauper has let the secret of her inimitable voice slip - she apparently relies on helium to help retain her 'squeaky' tones. The Girls Just Want To Have Fun star was spotted taking gasps of the gas - which distorts the voice to a much higher pitch - backstage before a gig as part of the Hetrick-Martin Institute benefit gala in New York last week (ends02Nov07). A source tells British newspaper The Sun, "It was like she was taking hits of the stuff but it certainly worked. She sounded like a chipmunk."