Ursula Vaughan Williams will be remembered chiefly as the second wife of Ralph Vaughan Williams. They were married in 1953, when Ursula was 41 and Ralph 80. Ursula cared for him without cosseting him, encouraging him to renewed activity both as a composer and as a leading figure in the musical life of Britain.

After his death in 1958 she devoted herself not just to preserving his memory but also to working tirelessly in musical causes that he had espoused, and above all to the encouragement and assistance of young musicians. Her dedication to that mission perhaps prevented her from achieving the degree of recognition she deserved as a writer and poet.

Joan Ursula Penton Lock was born in Valletta, where her mother's father was serving as GOC Malta, and her father (later Major-General Sir Robert Lock) was his ADC. She was brought up in army life. As a girl she heard very little music, and did not particularly enjoy what she heard. Her bent was towards literature and drama. In the early 1930s she became a student at the Old Vic. It was while she was there that she heard, and was overcome by, Vaughan Williams's music for the ballet Job, choreographed by Ninette de Valois. But she had not yet finished with army life: in May 1933, after leaving the Old Vic, she married Michael Forrester Wood, a regular officer in the Army, and from then on lived the nomadic life characteristic of army officers and their families.

By 1937 Ursula had written a scenario for a masque, which she plucked up the courage to send to Vaughan Williams, in the hope that he might compose music for it. Though at first he showed little enthusiasm for the project, he eventually agreed to meet her for lunch. Vaughan Williams, then aged 65, was expecting a matron in sensible shoes, and was agreeably surprised to meet an attractive, lively, energetic and impulsive young woman in her twenties. He enjoyed her company and respected her literary talent and judgment.

The meeting led eventually to their collaboration on words and music for what became the choral work Epithalamion, and for Ursula led to a deepening relationship as a loved and trusted friend not only of Ralph but also of his first wife Adeline.

Michael Wood died suddenly, of a heart attack, in 1942. He and Ursula had had no children, and Ralph and Adeline at once insisted upon Ursula coming to stay with them at their home in Dorking, Surrey. Ursula gave up the unpaid work which she had taken on for the St Marylebone Citizens' Advice Bureau, and took paid employment as a secretary-receptionist to a well-known paediatrician in London. From then on Ursula became a regular and increasingly frequent visitor to the Vaughan Williams home, often staying there and commuting to her work in London; and, as Adeline, increasingly crippled by arthritis, became less able to go out, Ursula was more and more often Ralph's companion at musical functions. She also became Ralph's unofficial literary adviser and collaborator, writing the words for his cantata The Sons of Light.

Adeline died in May 1951, and Ralph asked Ursula to manage his domestic affairs for him. When, some two years later, in February 1953, Ralph and Ursula were married, it seemed the most right and natural fulfilment of their long and affectionate friendship.

Ralph's activities had been increasingly restricted by his living at Dorking, the difficulties of travel, and the need never to be too far away from the ailing Adeline. After their marriage Ralph and Ursula moved to a house in Hanover Terrace in Regent's Park. This enabled Ralph to resume a larger role in the musical life of London, of which he became a kind of uncrowned king, a constant and welcome presence at all kinds of musical occasion.

He also produced a steady stream of new compositions: from this Indian summer of his life date such works as the Christmas cantata Hodie (for two numbers in which Ursula provided the words), a concerto for bass tuba and orchestra, a sonata for violin and pianoforte, the Ten Blake Songs for tenor and oboe, and the Four Last Songs (again with texts by Ursula).

After Ralph's death in 1958, Ursula moved to Gloucester Crescent, north of Regent's Park — a smaller house than Hanover Terrace, but still large enough for her to be able to have people to stay and to entertain, with a garden which she and her much loved cats could enjoy. Her main preoccupation in the following years was with the writing of Ralph's biography, published in 1964.

She did not attempt to describe or assess his music: that was left to a companion volume by Michael Kennedy. Nor did she attempt a direct assessment of his qualities and defects as a man; but by means of a thoroughly researched and well-written account of the events and activities of his life, supported by quotations from his correspondence with family and friends, she succeeded in conveying a rounded, vivid and objective portrait of that great and generous man.

She continued to write, publishing four novels and five volumes of poetry and providing texts for many other composers, including Herbert Howells, Malcolm Williamson, Elizabeth Lutyens and Elizabeth Maconchy (she wrote the libretto for her opera The Sofa).

But her considerable accomplishment as a writer was overshadowed by the musical side of her busy life. She was tireless in encouraging and supporting performances of Vaughan Williams's music; and it gave her especial pleasure when his opera The Pilgrim's Progress, which had been indifferently received when it was first performed at Covent Garden in 1951, was given a highly successful series of performances at the Royal Northern College of Music in Manchester in 1992.

During these years Ursula served on the governing body of the Royal Academy of Music and on the executive committee of the Musicians' Benevolent Fund. She became a patron of countless musical organisations and societies. Two years before his death Vaughan Williams had set up a trust, which he endowed with the royalties from his performing rights, with widely drawn objects for the advancement of music (so long as it was not his own) and the support of musicians. In the management of this trust Ursula played a leading part, and through it, as well as in many other more personal ways, she found outlets for her open-hearted generosity, particularly towards young musicians and those musicians who had been less blessed than Vaughan Williams with opportunities to get their music heard and appreciated.

A slight stroke towards the end of 1994, and a broken arm as a result of a fall the following year, inevitably led to some curtailment of her activities. But they did not dim her zest for life, her gaiety of spirit, her warmth in friendship, or her insatiable appetite for travel to distant places.

An autobiography, Paradise Remembered, which was praised for its charm and humour, was published in 2002.

Ursula Vaughan Williams, writer and champion of young musicians, was born on March 15, 1911. She died on October 23, 2007, aged 96