The ukulele is not an instrument you normally associate with the blues; nor is the blues section where you'd expect to find a Cyndi Lauper CD. Lauper's 11th studio album, Memphis Blues, combines both. "I found a really sick ukulele in a novelty shop with a metal top," she says, in her almost comically caustic Bronx-Sicilian drawl. "I tuned it to a chord and played it with a knife like the old guys did. I'm not fantastic – but I'm not fantastic at anything, except singing. And I don't really give a damn. I just love doing it. It's like the trombone. I make the dog jump when I play that."
Now 57, Lauper is preaching her conversion to the blues on a promotional schedule that ranges from an appearance on Radio 4's Woman's Hour to a spot on Later … With Jools Holland, with Holland accompanying her on the Lowell Fulsom classic, Shattered Dreams. It all seems a long way from the 1983 breakthrough hit, Girls Just Want to Have Fun, whose vocal style had less in common with Memphis Minnie than Minnie Mouse. Yet Lauper insists that the blues collection was the album she always wanted to make.
That ought to sound a warning: usually the album an artist announces they "always wanted to make" is the record none but the most forgiving fans want to listen to. But Memphis Blues turns out to be a triumph; packed with star turns from the likes of BB King, New Orleans pianist Allen Toussaint and rising blues hotshot Jonny Lang. Since its US release in June, it has been permanently lodged at the top of Billboard's specialist blues chart, and has become Lauper's biggest-selling album since 1986.
Even so, the shifting of a moderate 70,000 copies may be seen less as a measure of the album's success than an indication of how poorly the other records sold. In the mid-1980s, Lauper was neck-and-neck with Madonna as the world's top-selling female solo artist. Her debut, She's So Unusual, contained five top 10 singles and sold 13m copies. The follow-up, True Colors, did almost as well. But then she suffered burn-out, announced her retirement, and found that most of her original fans had lost interest when she changed her mind. The nadir came when her record company went out of business during the making of an album that never saw the light of day: the release date was penned for 11 September 2001.
Since then, there have been signs of a recovery. Bring Ya to the Brink in 2008 was a well-received trance album recorded in Sweden with collaborators including Basement Jaxx and Digital Dog. And she made a big impression in her home country with an appearance on the US version of The Celebrity Apprentice, from which she was fired by Donald Trump for insubordination: "In the end, I wouldn't get down and dirty," she says. "Everyone had a problem with me. I talk funny. I think weird. They said so many nasty things, it was like being back in high school."
She went down so well with television audiences, however, that there's now a reality series of her own in the pipeline. "The producers keep getting frustrated because I'm always off having meetings about other things," she explains. "I keep telling them, 'Sorry, but I couldn't say no.' So that's turned into the working title, Cyndi Lauper Can't Say No. It cracks me up the idea of the continuity guy going, 'This week on Cyndi Can't Say No' ... "
The 57-year-old Lauper turns out to be hardly any less restrained than the 27-year-old version, dressed in black rubberised leather with wild vermilion hair and metallic jewellery that looks as if it may have been assembled from parts of a chainsaw.
Lauper was never destined to grow old gracefully, though she has mellowed since she married actor David Thornton in 1991 (Little Richard presided at the ceremony). They've since had a son, Declyn, now 13. Yet the beauty of the blues is that it is one form of music in which artists are expected to improve with age.
"The album's partly about my getting older," she agrees, "but it really takes me back to where I started. I began by shouting Janis Joplin covers in an R&B band. That was my apprenticeship. And I had to go to Memphis to do this record, because that was the source. When I made my dance album, Bring Ya to the Brink, I went to Sweden and froze my ass off. But that's who I am. It's got to be the real deal or I won't do it at all."
How difficult did she find it to persuade blues royalty such as BB King to play on the record? "Oh, BB's a real sweetie," she purrs, "I just said to the producer, 'Let him play what the hell he wants – he's BB King!'" Was she intimidated about meeting him? "Well, I couldn't actually be there," she says, a little defensively. "But you know, I duetted with Sinatra once – and I never met him either."
Fans expecting a standard Cyndi Lauper album with a moderate blue rinse may be taken aback by what she has come up with. It's a flat-out, old-school blues record with all the raw edges showing: about as far from the slick production and Auto-Tuned vocals of modern pop recordings as it is possible to get.
"That's how I wanted it to be," she says. "The blues guys were the pop stars of their day. I chose songs that related to the times we're living in. Look at the state of the economy. The war. Katrina. People have the blues. They're hurting. So I just figured, an artist stands in the centre, looks around them and describes what they see. And at this point, the blues felt like the perfect way to do it."
European editions of the record contain, as a bonus track, a raucous, acoustic version of Ida Cox's feminist anthem, Wild Women Don't Get the Blues, on which Lauper cuts loose on Appalachian dulcimer and metal-topped ukulele. It's become her favourite track on the album. "It was women who originally popularised the blues," she points out. "Ida Cox wrote about staying out, getting drunk and kicking your man outdoors. It was the Girls Just Want to Have Fun of the 1920s."
Much as Lauper idolises the original generation of blues shouters, she now enjoys the status of an elder stateswoman herself. She's already gained the Lady Gaga seal of approval. The two singers appeared together earlier this year as part of the Viva Glam campaign, intended to raise Aids/HIV awareness.
"Yeah, Lady Gaga's cool," she says. "I was a big influence on her. We got together, splashed a lot of lipstick, raised a lot of money." And she is off: her train of thought diverted from the blues by her other great passion, the True Colors organisation for gay rights, which she established in 2007.
"There's still a civil rights struggle going on in my country," she says, "and it is for equality among the gay community. I can't stand idly by and keep my mouth shut while people are preaching hate. I'm friend and family (Lauper's sister Ellen is gay) and I'm also half-Sicilian, so am I gonna turn the other way? Not even a slight chance. So what can I tell ya? I'm edgy. I'm feisty. Take me or leave me. I ain't ever gonna change."
Memphis Blues is out now on Downtown Records.