Clare Deniz, who has died aged 91, was one of a handful of black Cardiff musicians to establish themselves in London two decades before Shirley Bassey. She played piano with the first established black British band, and, with her husband, formed an exciting wartime swing unit which drew praise from Glenn Miller.
Born in Cardiff, Clare grew up in one of only three black families in the Grangetown area. Her father, a Barbadian seaman, died when she was 18 months old, and she and her mother, orginally from Somerset, were taken in by Mrs Knight, a black woman who came from a Bristol theatrical family. Knight raised Clare with her own niece, and it was in this home that she was first exposed to music, playing piano and ukelele from the age of four. She took piano lessons, played her father's guitar, and, inspired by Louie Erskine, the boxer Joe Erskine's aunt, began to absorb modern dance music ideas.
Jazz had yet to make any impact in Cardiff, but "south seas" music was popular, and this, with quicksteps and the occasional calypso, were in the repertoire that, with three local guitarists, Clare played for church dances. On leaving school, she worked in a cigar factory, and, at the age of 16, began playing solo concerts with Waldini, whose famous Gypsy Band was a well-known attraction; later, he featured her band.
In 1936, Clare gave up the day-job to travel to London. With singer Don Johnson, a childhood friend, she joined guitarist Joe Deniz and two others for variety dates, pretending to be Americans.
Back in Cardiff, she married Frank Deniz, Joe's elder brother. In London for their honeymoon, they found rooms in Euston, before joining forces with two other black Britons to move around Soho, taking whatever work came up. They played at such "bottle-parties" as Hell's Kitchen and the Padded Cell - sometimes just in exchange for a meal - and familiarised themselves with the music and mores of places such as the Nest, where visiting Americans jammed.
The Trinidadian drummer Happy Blake provided Deniz with her first residency. At his Rendezvous des Artistes, she met the musicians from Ken "Snake Hips" Johnson's new, all-black band, with which her brother-in-law played guitar. When the pianist left for Australia, Deniz took his place at Mayfair's Florida Club, staying until the birth of her first child.
As a black woman moving in snobbish circles, Deniz swiftly recognised the need to comport herself with dignity; she had stylish dresses and tailored costumes made for her, and bought the best accessories she could afford. Such behaviour was important for black artists establishing themselves in prewar days, but, although she was seen by some as a fashionable adjunct to her husband, as a pianist she frequently worked more than Frank, the guitar being an optional instrument.
Show business had its startling moments. Playing at a smart Kensington club, Deniz once felt hot breath on her back, and turned to look into the eyes of a pet leopard on a chain. On another occasion, she was rescued from a first-floor ledge in New Compton Street, when the building where she was playing caught fire; all she remembered afterwards was her ruined silk stockings.
With Frank on war service at sea, Deniz played with musicians such as bandleader Eric Winstone and trumpeters Johnnie Claes and Leslie Hutchinson. She consolidated her reputation in the jazz world as a competent, reliable pianist when she joined the West Indian Swing Stars, featuring Bertie King's elegant saxophone, bassist Coleridge Goode and the innovative guitarist Lauderic Caton. This was followed by time with Frank's Spirits of Rhythm, a driving sextet modelled on Benny Goodman, with Jimmy Skidmore on tenor saxophone.
The birth of Deniz's second daughter, in 1945, slowed down her career. In 1951, she found herself trying to play bebop with Jamaican arrivants trumpeter Dizzy Reece and saxophonist "Pet" Campbell, and, while she confessed herself at odds with the new music, the experience left her determined to improve and update her playing.
She renewed contact with Don Johnson, their musical relationship taking them from a Chelmsford leper hospital to a north London pub, where she stayed for seven years. She sang in Fela Sowande's choir for the 1954 television series Club Ebony, but, by the 1960s, considered herself in retirement until a friend found her another pub job in Tottenham. There, she enjoyed herself, playing everything from Scott Joplin to Oscar Peterson.
Deniz continued to work into the 1980s before moving to Malaga, where she and Frank played occasionally in local bars. They returned to England when her health began to deteriorate, and she developed Parkinson's disease. Frank, her devoted husband of 66 years, survives her, as do their daughters, Lorraine and Claire.
· Clare Ethel Deniz, musician, born September 30 1911; died December 7 2002