Most performers do their best to sing as well as possible on stage. But what if the part calls for singing opera really, really badly? Is that difficult?

"No! Not if you're not an opera singer - it's not hard to sing badly at all," says Diana McLean, last seen at the Q in 4000 Miles.

She is touring in Glorious! as Florence Foster Jenkins, the American socialite and amateur opera singer once dubbed "the first lady of the sliding scale". Foster Jenkins' voice earned her a cult following in New York City, culminating in a sold-out performance at Carnegie Hall in 1944 from which it was estimated 2000 people had to be turned away. She died a month later at the age of 76.

For the curious, Foster Jenkins made recordings - which can be found online - and as McLean says, her voice is "abysmal - it's simply a terrible noise. She's underneath the note."

Whether singing standard repertoire such as the Queen of the Night's aria Der Holle Rache from Mozart's Die Zauberflote, operetta like Adele's Laughing Song from Die Fledermaus or one of the art songs she wrote lyrics for to music by her longtime accompanist, Cosme McMoon, she committed all kinds of crimes against music - poor diction, tempo, rhythm, you name it.

"When she can't hit the note she just screeches."

Accounts vary as to how self-aware Foster Jenkins was about her talents, or lack thereof. Many have said she was genuinely deluded, but she performed recitals only occasionally to select audiences and sold tickets herself, questioning would-be purchasers to make sure they weren't music critics. And then there's her often-quoted remark - "People may say I can't sing, but no one can ever say I didn't sing" - suggesting she was all too aware of her detractors. But she carried on regardless, right up to the end.

McLean is joined in Glorious! by Josh Sanders playing McMoon, her loyal if sometimes befuddled accompanist, and Kaarin Fairfax as various representative women both loyal and hostile to Foster Jenkins.

"Florence ran off and got married at the age of 16 or 17," McLean says. Born in 1868 to a wealthy Pennsylvania family, she eloped with Dr. Frank Thornton Jenkins to Philadelphia in 1885 when her father refused permission for her to study music in Europe.

"She was an accomplished pianist," McLean says.

That talent was to come in handy: she contracted syphilis from her husband and left him trhe year after they wed but kept his name and it's unclear whether they ever divorced. The treatments for the disease might have given her tinnitus which could be responsible, in part, for her vocal shortcomings.

An arm injury ended her piano-playing aspirations but she supported herself by giving piano lessons as her father refused to help her although by the time of his death in 1909 he had relented and left her a sizeable trust fund. By then, she had moved to New York and taken up with a British actor, St Clair Bayfield in a co-habitation relationship that provided her companionship although he lived in a separate apartment and had other women.

"He was very good to her, very protective of her - he saved her from being troubled by people who wanted to get at her."

McLean says the family money was useful in more ways than one.

"She bought her way back into society - she started the Verdi Club to sing opera in English,". That was in 1917 - by then she had already been giving her private vocal recitals for five years. Her fans included celebrities such as the tenor Enrico Caruso and the songwriter Cole Porter.

McLean isn't a stranger to bad singing. In the 1960s one of her jobs was imitating then-popular singer Mrs Miller - who had a cult following for much the same reasons as Foster Jenkins - for a Mobil ad.

And despite her earlier protestations, it seems that there is an art to singing badly on purpose. McLean says when she was rehearsing Glorious! the director had to stop her a few times for singing too well.

"I had to flatten it down," she says.

But she doesn't mind.

"I want to do the worst job I can with it."