When Gal Costa sings at the Royal Festival Hall next Tuesday, things will be different. Following an established pattern of summer Brazil bonanzas in London since Caetano Veloso's visit in 1993, Gal (as she is known in her own country) will be received with rapture by Brazilian ex-pats who come out in force for this sort of event, sing along, and crowd in an adoring mass at the foot of the stage. Stars like Gal take Brazilians home faster than a Varig flight to Rio.
Gal sang for the first time in London last year with Caetano Veloso, and two other contemporaries from Salvador da Bahia (in north-east Brazil), Gilberto Gil and Maria Bethania. It was their first reunion in 20 years, and poignant for Gal because of the presence of Caetano and Gil. The two men had spent three years in London, in exile from Brazil's military regime, between 1969 and 1972, high on tropicalism - a wacky hybrid of Brazilian styles and western rock.
"While they were in exile," she says, unexpectedly soft-toned for a woman with such a big voice, "I sang their songs a lot in Brazil. I also visited them three or four times. I was determined to keep alive what they stood for. I was a tropicalista in spirit."
Gal had not been back to London since that period. Today, touching 50, she is still a passionate exponent of Caetano's music; he in turn has composed many songs for her.
"Caetano is the one Brazilian composer who knows how I sing - we have a very strong musical identification."
She is equally close to Chico Buarque, the other major name in Brazilian singer / songwriting of the last 30 years. The concert she's currently touring Europe with features Caetano's and Buarque's songs exclusively. It's an intoxicating mix: the sexy stage presence of Brazil's premier female voice belting out numbers by arguably the two most melodically inventive pop-songwriters since Lennon and McCartney.
Gal has no obvious musical pedigree, other than coming from Salvador da Bahia. Her parents were already separated when she was born - her father, a hit-and-miss businessman, remarried and had seven more children. He died when Gal was 14 and already determined to become a singer. Her mother brought her up alone.
In the early 1960s, Gal went to Rio, home of the bossa nova. But Gal found it hard to make headway at first: "When you start as a singer in Brazil, you realise there are far more male singers than female," she says. Still, she had some impressive role models - Sarah Vaughan, Billie Holliday, Ella Fitzgerald - and made her professional debut aged 19.
By the end of the 1960s, she was on the map. Her ticket to fame was a startling voice, smouldering good looks and, above all, the songs of Caetano - his name in Brazil rang with the status of legend. Gal became a full- blown tropicalista.
Never politically engaged, unlike Buarque and others, Gal was not averse to causing a stir or two: a 1974 album cover depicting her topless had to be sold wrapped in black plastic. "My only brush with the authorities," she recalls, smiling.
Ten years later, with 15 albums to her credit, Gal was nominated by Time magazine as one of the grand "divas' of pop, alongside Whitney Houston and Kate Bush. This followed her album Profana. Does she enjoy being being ranked alongside international stars? "I've always striven just to be natural and innovative," she says.
What about her being female in so male-dominated a business? "I'm not a feminist, but I think a woman can bring more expression into the world. It's difficult, because we do live in a macho world - but being a woman is just fine."
n 7.30pm Tues, RFH (0171-928 8800)