Time magazine called singer Marni Nixon "the Ghostess with the Mostest". Although her face wasn't well known, her voice certainly was: the American soprano had a long and busy career in films as a vocal double, dubbing, in whole or in part, the singing voices of such stars as Sophia Loren and even Marilyn Monroe (the high notes in Diamonds Are a Girl's Best Friend in Gentlemen Prefer Blondes).

She was not credited for such assignments – indeed, she was told if she talked about it publicly, she would never work again, Her biggest dubbing jobs were in three Oscar-winning musicals, singing for Deborah Kerr in The King and I (1956), Natalie Wood in West Side Story (1961) and Audrey Hepburn in My Fair Lady (1964). Word, inevitably, did get out about her work, and Kerr said in an interview she wished she could sing like Nixon.

Nixon did make occasional film appearances, most notably as Sister Sophia in The Sound of Music (1965), sang a credited role in the Disney animated film Mulan (1998) and has had a long career on stage in operas, cabarets, musicals and concerts. She toured with the pianists Liberace and Victor Borge, made recordings of cabaret and classical repertoire and in 2006 published an autobiography, I Could Have Sung All Night. She is still alive, aged 85.

Australian singer Melody Beck, a long-time fan, has prepared a show, Unseen, that pays tribute to Nixon's versatility and talent in singing for a variety of stars. Beck has has met, performed for and even received coaching from Nixon herself, who became a friend.

Beck says, "I'd always watched the films – West Side Story, My Fair Lady, The King and I – growing up – and my Dad would sometimes point out, 'That's actually Marni Nixon singing – it's not really Natalie Wood, it's not really Audrey Hepburn'.''

She was fascinated. After graduating from the University of NSW with degrees in both music performance and theatre studies and winning the Your Theatrics International Cabaret Contest she prepared and began touring Unseen to cabaret festivals in Australia in 2014 and to New York. In it, she performs in character as Nixon, running through her Hollywood career as a ghost singer and performing some of the songs she sang for others in the movies.

Beck says Nixon's relationships with the stars varied. Some, like Kerr, were gracious and Nixon was able to work with them during pre-recording of the songs while others, such as Wood, were under the impression they were going to do most of their own singing and Nixon had to re-record the vocals and match the on-screen lip movements, a more difficult task.

While she focuses on the big three movies and their songs there are other byways to explore, both in story and song. Nixon voiced an animated goose in the movie Mary Poppins – which, as is well known, Julie Andrews took on when she lost the role of Eliza Dolittle in My Fair Lady to Hepburn.

"Marni did an album of the Mary Poppins songs with Bill Lee, who dubbed Christopher Plummer in The Sound of Music."

One of her earliest jobs, when she was 19, was dubbing child actress Margaret O'Brien, then 12, in a lullaby in the film The Secret Garden (1949).

And what did Nixon think of Unseen?

"She really enjoyed it – she said it was very audacious, with a little smile and a twinkle in her eye," Beck says.

"She was so kind and wanted to help out."

Beck says her voice was similar to Nixon's when the latter was younger and the singer gave her a CD of a show she had done about her life. One aspect of the show that had concerned Beck was delving too deeply into Nixon's personal life, which had its share of difficulties. The singer was married three times, including to Oscar-winning film composer Ernest Gold (Exodus), divorced twice, and was widowed last year after a long marriage to the man Beck says was "the love of her life". Her son Andrew Gold, a musician whose songs included Lonely Boy and Thank You For Being a Friend, used as the theme for the 1980s sitcom The Golden Girls, died in 2011 at the age of 59.

"But she said, 'Put in whatever you want'.''

Unseen will be her Canberra debut. She says she heard about Teatro Vivaldi from pianist Martin, an old family friend, who'd worked there with performer Amanda Muggleton, and is looking forward to performing in the national capital for the first time.

Beck grew up in a musical family performing in amateur Gilbert and Sullivan productions. Since her graduation, apart from Unseen, Beck's credits have included a number of stage musicals in Sydney and she is writing a couple of new shows, one with Bernard Lagana based on the careers of John Dankworth and Cleo Laine and another about the star Rita Hayworth.

"She had dubbers for every one of her films. She had four main dubbers throughout her life – Marni wasn't one of them."