The pianist Yaltah Menuhin, who has died aged 79 after a heart attack, was the younger sister of Yehudi, the violinist, and Hephzibah, also a pianist. While Hephzibah was one of Yehudi's most constant musical partners, Yaltah took a separate path: she sometimes performed at the Bath festival, which Yehudi directed during the 1960s, and recorded one Mozart slow movement with him, but she also made an independent career in the United States.
Named after the Crimean resort, Yaltah was born in San Francisco to the Russian-Jewish parents, Moshe and Marutha, whose musical gift to the world is vividly evoked in Menuhin, Humphrey Burton's biography of Yehudi, published last year.
Touring internationally in the wake of Yehudi and his parents, the two sisters were, like him, kept away from schools, but they all learnt European languages from tutors and acquired a sophisticated culture, as well as their musical education.
At the age of 15, Yaltah was composing proficient French alexandrines about her dreams and crushes. Rudolf Serkin, who taught both sisters the piano as small girls, thought Yaltah the more talented.
But, in temperament, she was less robust than Hephzibah, who fought more successfully against their parents' reluctance that either should have a musical career, and who was so close to Yehudi that Yaltah was made to feel an awkward third.
When Yehudi and Hephzibah both decided to marry into a prominent Australian business family, Yaltah was 16, and was allowed by her parents to marry a lawyer from St Louis. The marriage lasted for only a year, and was an extremely painful experience for her; recriminations with her parents were such that, during the last 30 years of her mother's life, she refused to see her daughter.
Yaltah was a sensitive and revealing pianist, and, during a period in Los Angeles, became more engaged with contemporary music than the musically mainstream Hephz- ibah. She was fortunate in her third marriage, in 1960, to a gifted American pianist, Joel Ryce. He later retrained as a psychotherapist, and became well respected in Jungian circles; they settled in west Hampstead.
A high-water mark in the tide of the Menuhins was reached in 1966, when Yehudi conducted his sisters and his youngest son, Jeremy, in Mozart's three-piano concerto at his 50th birthday concert in London. Soon afterwards, Yaltah's main priority came to be supporting Joel in his new career. In 1981, Hephzibah died of cancer; Joel died in 1998, shortly before Yehudi.
During the last year of her life, Yaltah enjoyed a late musical re-flowering, which included a touching performance of Mozart at the Queen Elizabeth Hall, with a young violinist from the Yehudi Menuhin school. At her last recital, at Orwell Park school, Ipswich, only a week before her death, she gave a taxing programme of preludes by Chopin and Debussy.
Blessed with long golden hair, Yaltah developed a distinctive dress sense, with wispy gold embellishment and faint overtones of druidism. Her home, and her letters, were all in keeping, and late in life she began to make charming icon-like paintings on wood panels.
She was a determined original, tireless in reaching out to feed, comfort, heal and advise. Yehudi wrote of her in his autobiography that she was "reaping the rewards in kindness and gratitude that life has otherwise denied her". The two sons of her second marriage, to Benjamin Rolfe, survive her.