Sir Michael Tippett, OM, CH, CBE, died on January 8 aged 93. He was born on January 2, 1905.

The extraordinary youthfulness of appearance which Sir Michael Tippett retained into extreme old age, even when frailty overtook him and when eye problems had led to near-blindness, was a true reflection of his mind. To the end, he was a rare example of a composer whose sensibilities were alert to all generations and to many cultures. Though possessing great certainty of moral belief, and including in his character a vein of formidable determination, he was the most responsive and enchanting of companions, especially with the young. This openmindedness to new and unorthodox ideas was part of his optimism; he believed that change did not necessarily mean decay. His talk, whether in private or in public, could produce a golden haze of ideas shot with penetrating lightning flashes. He could praise or deplore his own music as if he were more its vessel than its maker. In times when artistic certainties have been hard to come by, Tippett was an artist who diffused positive ideas into all who knew him or were affected by his music.

Together with Benjamin Britten, Tippett was one of the two most significant English composers to come to maturity during the Second World War. Britten's senior by nearly nine years, Tippett was slower to mature; and though he wrote much music in the early 1930s, it was not until the Concerto for Double String Orchestra of 1939 that he began to make a major reputation. This was clinched with the performance of A Child of Our Time in 1944.

It was in this remarkable oratorio that Tippett first declared the convictions which were to grow and take manifold expression in his music. The occasion of the work was the murder of a Nazi diplomat in Paris in 1938 by a young Jew, and the subsequent pogroms in Germany that included the so-called Kristallnacht; but Tippett took the incident as the starting point for a work declaring pacifist beliefs and a deep hunger for reconciliation at all levels of human relationships. Later he was to acknowledge the oratorio as a key work, and to claim as its essential sentence, "I would know my shadow and my light; so shall I at last be whole."

Michael Kemp Tippett was born in London, the second son of a lawyer of Cornish origin. He was educated at a prep school in Swanage, at Fettes College, and much more happily at Stamford Grammar School, before going to the Royal College of Music in 1923. Here he studied composition with Charles Wood (privately exploring Renaissance music and the English madrigalists), piano with Aubin Raymar, and conducting with Malcolm Sargent and Adrian Boult. He conducted a madrigal group and a musical and operatic society in Surrey; but after a concert of his own music in 1930 left him dissatisfied (despite an appreciative Times review), he returned to the college for further study with R. O. Morris, whose musical sympathies lay close to his own and who helped him to develop his own technical interests.

He gained further musical experience working among unemployed ironstone miners in Yorkshire; and this also served to deepen his political convictions. In 1932 he became conductor of the Morley College Orchestra, formed to help out-of-work musicians; he also conducted choirs associated with the Labour Party.

Briefly a member of the Communist Party in 1935, he found his Trotskyist leanings unwelcome, and his deepening pacifism led to a gradual disillusionment with politics. A play he wrote, The War Ramp, confronted the conflict of political idealism and pacifism, but it was a course of Jungian analysis that helped to stabilise him, and introduced him to the concept of "shadow" and "light" in a single psyche.

Tippett's own music of these years included a string quartet and a symphony (withdrawn) and in 1937 a setting of another profoundly influential artist, Blake, A Song of Liberty, reflecting his dismay at the darkening European scene.

His humanitarianism was practical as well as idealistic. He made himself a worthy successor to Holst at Morley College, working inspiringly among groups with little normal access to great music; and in the war his total pacifism brought him a three-month prison sentence, which he bore with courage and humour. He had meanwhile won a loyal following at Morley and among a widening circle of friends and sympathisers.

Although a challenger of received order, Tippett was also a traditionalist. Rejecting the romanticism of Elgar no less than the folk-song revivalism of Vaughan Williams, he followed Holst's example in turning to earlier English sources for his music. Purcell was an inspiration as well as the madrigalists, whose "sprung" metres, nimble dance rhythms and rich counterpoint became increasingly fertile soil for the growth of his own idiom. His attraction to popular music, especially to the blues, gave him familiarity with jazz, and provided one of the most effective ingredients in A Child of Our Time. Cast as a Bachian oratorio to his own words (on the advice of T. S. Eliot), the work includes five Negro spirituals set like chorales in the structure; and this device, movingly handled, helped to draw listeners to the work. His Second String Quartet had meanwhile greatly impressed musicians with its confidence and originality.

However, the complexity which was an outcome of a widely-ranging, riskily over-receptive mind proved confusing when a new symphony (now known as No 1) was performed in 1945. Later it became clear that one difficulty which stood in Tippet's way was unfamiliarity with his style among performers, and often inadequate rehearsal. Tippett himself, though an enthusiastic and popular conductor, was not always his own best advocate; he was better served by others including Walter Goehr, John Pritchard, later and above all Colin Davis.

The production of Tippett's first opera, The Midsummer Marriage, in 1955 brought to the fore controversy about a self-defeating complexity of thought and means. The text he provided for himself contains the oddities of expression and the somewhat gauche colloquialisms for which he had a weakness, but they pass the crucial test of furnishing their composer with the right stimulus for the right music. His long absorption in Jung and in Frazer's Golden Bough was not conducive to clarity, but it did serve to release music of a richness, a lyrical profusion and a radiant ecstasy that he had not expressed so fully before. The Ritual Dances from the opera quickly became a popular concert item. Belonging to the same music phase are the song-cycle The Heart's Assurance and the Piano Concerto (1956).

In an effort to elucidate his ideas, Tippett wrote and broadcast a number of articles, some of which were published as Moving into Aquarius and Music of the Angels. They reveal, no less than the music, a mind of wide and deep sympathies, stocked with a curiously assorted profusion of ideas that was nevertheless rich and stimulating. His Second Symphony (1958) sprang from a piece of Vivaldi used, he declared, as an archetype, though the outcome was entirely personal, developing many of the rhythmic and melodic ideas that had become by now fingerprints of his style. In 1959 he was appointed CBE.

With his second opera, King Priam (1962), Tippett turned to a classical myth instead of one of his own making. In part responding to earlier criticism, his idiom became sparer and tauter; the orchestration is harder and brighter; instead of flowing in self-generating profusion, the music is constructed in opposed blocks of sound. The work is more traditional in aspect, containing novelties of construction and some original coups de théâtre. It is the central work of a period that also included the Songs for Achilles, the Second Piano Sonata (1962) and the Concerto for Orchestra (1963).

With The Vision of St Augustine, written in 1966 - the year in which the composer was knighted - Tippett produced his first major choral work since A Child of Our Time. The music is once more highly complex, but with a novel drive and urgency.

Tippett's third opera, The Knot Garden, followed in 1970. Rather than Priam, it is this work which renews the preoccupations of The Midsummer Marriage. Tippett himself proposed that, if the earlier work invoked the quest theme of The Magic Flute, here the analogy was Così fan tutte. It is a comedy, treating the repair of a marriage by an older man who sets up a dramatic fiction so as to mend the troubled relationship, the man grown too mundane, the woman too ethereal. The theme is broadened, however, to include the need for reconciliation, through deepened self-awareness, between those confronting one another across gaps that are political and racial as well as marital. The music, which includes a large set-piece blues, is at once tauter than the first opera and more lyrical than Priam.

Out of this opera's archetype came Songs for Dov. One of the work's characters, Dov, is left bereft of a relationship, and the Songs chart (in a wealth of quotation and literary allusion) his journey of self-discovery. There soon followed the Third Symphony (1972). Here, asking himself whether there is still validity in the moral certainties of Beethoven, Tippett moves from quotation of the Ninth Symphony to a statement of a new kind of moral confidence. The opening movement is one of the most powerful in modern symphonic literature, and if the concluding songs (to Tippett's words) may not sustain the weight of certainty, they provide a lyrical conclusion comparable to Beethoven's own final invocation of song in the Ninth. The Third Piano Sonata is lighter but virtuoso and in the same vein of vigorous affirmation.

Tippett's fourth opera, The Ice-Break, reached Covent Garden, the scene of all his previous operatic premieres, in 1977. Here the plot, on the return of a released political prisoner to his wife in a new country, broadened the reconciliation theme further to encompass the reunion of sundered East and West, old and young, black and white. A laconic but still lyrical work, it reflected the undimmed artistic exuberance and moral fervour of an artist now in his seventies.

By the time of the opera's premiere, Tippett had already completed his Fourth Symphony, in which a new approach is made to the problem of balancing the abstract and the dramatic. Though the structures are close and elaborate, the "programme" moves from birth to death, deriving from a film Tippett had once seen showing a foetus growing inside an animal's womb. A taut, powerful work lasting half an hour, it further confirmed Tippett's stature as the most original symphonic thinker of his generation.

Hardly was the work finished when Tippett embarked upon another renewal of traditional forms with his Fourth String Quartet (1978). Like the Fourth Symphony, it is cast in a single movement; and the archetype here is the birth to death image, moving from stillness through energy and conflict towards a new condition of stillness. In a sense, both works preface the Triple Concerto of 1979, the year in which he was appointed a Companion of Honour. A piece for violin, viola and cello with orchestra, this has an ancestry in Brahms's Double Concerto but also includes references to Balinese music.

Still more, these works preface The Mask of Time (1984), a dramatically conceived work for soloists, chorus and orchestra filling a whole concert. Though written to his own text, it draws on Milton and Shelley: Part 1 is a creation myth; Part 2 considers Man and time in an historical context. Tippett declared that he hoped "to offer fragments or scenes for a possible 'epiphany' for today". There were, as ever, those who found confusion in the presentation, for all the attraction they felt to some beautiful and ambitious music. Other contemporary works include a bold, powerful Fourth Piano Sonata, a searching piece for Julian Bream deriving from Wallace Stevens's The Blue Guitar, a Fifth String Quartet and a Festal Brass with Blues for Hong Kong.

Sir Michael Tippett was appointed to the Order of Merit in 1983. His 80th birthday, two years later, was widely celebrated with concerts and tributes. Though he underwent major surgery in 1987, he resumed work on his fifth opera, New Year (1989). Set in a modern Terror Town visited by a space pilot from the future, it renews long-held concerns in the choice presented to a fearful heroine, that of turning her back or of facing hard self-realisation. The score incorporates electric guitars and saxophones, using them to absorb a rock music manner into Tippett's own idiom without loss of its capacity for magical invention. It was premiered in a co-production between Houston Grand Opera and Glyndebourne.