Mstislav Rostropovich was one of the great cellists of the age, indeed in the history of the instrument; and like some others, including his old master, Casals, he was a musician whose abounding talents burst out into other activities both musical and humanitarian.

As a cellist he was comfortable in both standard classical-romantic works and modern repertoire, which he enriched with significant commissions from world-class composers, while the pianistic and conducting talents that flowered after his enforced departure from the Soviet Union revealed further facets of a protean musical personality.

He also strode the world stage in a nonmusical capacity, as an ambassador for humanitarian causes, publicly defending his dissident friend Aleksandr Solzhenitsyn and organising an impromptu concert when the Berlin Wall fell. Latterly he and his wife set up a foundation to provide free health care for destitute children.

Mstislav Rostropovich was born in Baku, Azerbaijan, in 1927. Like his father, Leopold, a Casals pupil who was also a distinguished international cellist, Mstislav first studied the piano, with his mother, and only later, at the age of 10, the cello, with his father. As a child, he also began to experiment with composition.

During the war the family moved to Orenburg, where Rostropovich completed his formal education and gave his first public performances, duetting with his sister, making local tours with the band of Leningrad’s relocated Small Opera Theatre and, at the age of 13, playing the Saint-Saëns concerto with the Ukrainian orchestra at Slaviansk.

At the Moscow Conservatoire, which he entered in 1943, his curriculum was dominated by cello studies with Semyon Kosolupov, whom he later credited with having made “a master of me with perfect command of the cello”, and composition with Shostakovich. Rostropovich’s creative as well as executant gifts had already been aired at Leopold Rostropovich’s final recital, shortly before his death in 1942 at the age of 50, in which the pianist son accompanied the cellist father in the former’s newly composed cello concerto.

The childhood appearances had drawn attention to an exceptional talent, and in the years after the war he began to appear in concerts in other countries with resounding success. He took first prizes at the international music awards of Prague and Budapest in 1947, 1949 and 1950, the same year in which he was awarded the Stalin Prize. He then studied further, with Casals, and by 1953 was lecturing at the Leningrad and Moscow conservatories.

Rostropovich was first heard regularly in the West in the 1950s. His powerful musicianship, together with his extraordinary technical command and the vital personality that went with it, won him an immediate following. He seemed equally at home in Bach or Vivaldi, Haydn or Beethoven, Dvorák or Strauss, or modern works, of which many, including concertos and solos by Shostakovich, Prokofiev, Khachaturian, Britten, Lustolawski, Penderecki, Dutilleux, Schnittke and Sir Arthur Bliss, were written for him. Though in private he was outspoken about some of the Soviet music he played, at this stage he felt it his duty to act as an ambassador for his country, and did so cheerfully and loyally.

In England he was a particularly welcome guest. He debuted at the Festival Hall, London, in 1956 with the Dvorák concerto and was an instant success with both public and critics.

Benjamin Britten, hearing him for the first time in a radio broadcast in 1960, thought that Rostropovich’s was some of the most extraordinary cello playing he had ever heard, a judgment confirmed a few days later when he saw him at the Festival Hall in Shostakovich’s First Cello Concerto.

The Britten connection deepened into a profound musical friendship. For Rostropovich, this was the source of a series of works for him to play; for Britten, it was the inspiration for instrumental music after a long concentration on vocal and choral music and some well-documented travel opportunities.

The immediate fruit of what also became a devoted personal friendship was the Cello Sonata; the largest outcome was the Cello Symphony, premiered in the Soviet Union (to an audience of excited youth and more wary elders) in 1964. In the following year he gave a cycle of concerts in London at which he played leading works in the repertory from Vivaldi to Shostakovich.

In 1955 Rostropovich married the Bolshoi soprano Galina Vishnevskaya, and thereafter he made frequent appearances as an excellent pianist in her recitals, which often featured Russian song rarities little known in the West.

He also developed, with rather less success, a career as a conductor: the warmth of his musicianship, always powerful but strongly controlled as cellist and pianist, seemed to grow somewhat self-indulgent on the rostrum. However, he made some successful recordings, especially of opera, and appeared regularly with the LPO and from 1977 to 1994 he was musical director of the National Symphony Orchestra of Washington. He also conducted Tchaikovsky operas at the Aldeburgh Festival, of which he became a director, assuming a leading role in its affairs after Britten’s death in 1976.

Never a personality to be easily constrained, Rostropovich inevitably came increasingly into conflict with the Soviet authorities. His exuberant lifestyle was more easily tolerated than his outspokenness, and though he remained a valuable musical ambassador (and popular with his fellow musicians), matters came to a head over his championship of Solzhenitsyn. He refused to deny the writer hospitality in his Baltic dacha, and when in 1970 he attempted to publish an open letter of protest at cultural restrictions, his own freedom to travel was curtailed.

In 1974 he and his family were permitted a two-year stay abroad. It was intended as a cooling-off period but the excuse of his outspokenness was found to deprive him of his Soviet citizenship. This he found a hard blow. He and his family settled in the US – a country that, ironically, had greeted his debut in 1956 with an almost empty Carnegie Hall.

Thereafter, until the collapse of the Soviet empire, he was the subject of public indifference in official Russia, a “nonperson” barely rating mention in reference books, though the continuing object of private interest and warmth among old colleagues.

In exile his international prominence as a cellist, pianist and musical ambassador increased, as did his conducting engagements. With the accession of Gorbachev in 1980 reconciliatory overtures were made but declined by Rostropovich, who, however, did return to Russia without a visa to support the President when he was removed from office in 1991. After that more cordial relations with his homeland were established, and cemented by the purchase of homes in Moscow and St Petersburg and the establishment of the Vishnevskaya-Rostropovich foundation for sick children.

Rostropovich was an artist of extraordinary powers, as may be heard from his many recordings. His determination was formidable: on the rare occasions when he seemed out of sympathy with a musical occasion, this quality could bear almost ruthlessly upon a work. But it was the energy and warmth of his character that far predominated, and marked his performance, and this was expressed with an astonishing range of technical skill. His tone was strong and well-focused, ranging from a delicate whisper by way of sonorous richness to an attack in all registers of ferocious strength. His fingerwork was dazzling, yet he never indulged in virtuosity for its own sake, and greatly preferred the Bach solo suites (which he played with memorable inward intensity) to flashier favourites.

His numerous awards included appointment as honorary KBE in 1987.

Rostropovich is survived by his wife, Galina Vishnevskaya, whom he married in 1955, and by their two daughters.

Mstislav Rostropovich, cellist and conductor, was born on March 27, 1927. He died on April 27, 2007, aged 80