MUSIC / Young man's fancy: Bayan Northcott re-examines the impact of Johannes Brahms in the light of an upcoming South Bank series of his early music

Brahms for maturity? The sober colouring and compositional cogency of the music, the patriarchal persona and solitary dedication of the man himself, have often been construed as the ultimate in artistic wisdom - rarely more richly communicated than in the late Clarinet Quintet of 1891. Yet in the middle of its autumnal, classically structured slow movement, the clarinet suddenly launches into a strange, restless improvisation in Hungarian Gypsy style. Even Hans Keller, who considered Brahms's mature restraint often reflected emotional inhibitions, was prepared to concede that the passage must have been written 'under exceptional psychological conditions'. Less sophisticated listeners might wonder whether Brahms was looking back in almost wild nostalgia at his footloose youth; even asking himself, in his lonely eminence, if things could all have turned out differently.

Whether or not his musical training in his obscure Hamburg childhood had been as hand-to-mouth as he sometimes later suggested; whether or not he saw more than was good for him in the dockside dance halls where he played for his teenage pence, his life had already moved into its most tumultuous phase by the time he was 20. It was spring 1853 when he first left home, armed only with a formidable piano technique and a satchel full of ambitious early scores, on an informal recital tour with a dubious Hungarian violinist called Remenyi. Within weeks, he had met and sealed a lasting friendship with his brilliant contemporary, Joachim, and had been received, if less propitiously, by Liszt - apparently falling asleep while the great man was playing to him. That September, he turned up on the Dusseldorf doorstep of Robert and Clara Schumann. A month later, the enraptured Schumann hailed him in Germany's most influential musical journal as an already achieved master 'fated to give expression to the times in the highest and most ideal manner'.

No sooner were such extravagant expectations thrust upon him than Brahms lost his new-found father-figure with Schumann's removal to his fatal asylum, and found himself increasingly involved with Clara. Whether the 14-year age difference between them or Clara's reluctance to have yet more children was decisive in precluding their marriage after Schumann's death, their continual closeness seems to have complicated Brahms's relations with other women, culminating in the painful breaking-off of a promising engagement when he was 25. A year later, an anti-Liszt polemic he and Joachim were planning was prematurely leaked to the press, attracting further controversy. The longer-term effects were predictable. By his early thirties, the slim, fair-haired, ardently romantic youth who had presented himself to the Schumanns was already giving way to the stocky, caustically self-defensive - if as yet beardless - figure of the later years, and Brahms had begun to settle into his lifelong bachelor round of long creative summer holidays and Viennese winters of performing and studying - as insulated as possible from further public or private upset.

Despite his increasing artistic self-consciousness - famously epitomised in his withholding of the First Symphony until he was 43 - Brahms's last three decades were to prove colossally productive. Yet had he died, like Schubert, as young as 31, we would surely still remember him for a dozen repertory pieces. Next Friday, the South Bank begins a five-concert mini-series, programmed by Roger Vignoles and consisting, with one exception, entirely of works Brahms completed before 30; the exception being the Piano Trio No 1 in B major, a unique instance of the old Brahms re-composing a work of his youth - published, significantly, around the same time as the Clarinet Quintet. It is often held that Brahms's idiom remained pretty constant over his career; that his development comprised an enriching of skill and content rather than an evolution of language. Yet, if we can no more than vainly fantasise what Schubert might have written had he lived as long as Brahms, the Young Brahms series at least invites us to consider how startlingly different his early works might now seem had he been cut off as prematurely as Schubert.

For a start, we ought to be newly impressed by their daring, as the earliest critics were - blissfully unaware of the conservative ticket music history would later pin upon him. 'These works are new, bold, large and beautiful - but also very, very difficult to understand and perform,' proclaimed one reviewer. And already in the characteristically chunky Scherzo, Op 4 for piano composed at 18 and the three massive piano sonatas - Schumann called them 'veiled symphonies' - completed by 20, Brahms emerges as an original sensibility: carrying forward Beethovenian procedures with a confidence in marked contrast to the later deference he would develop towards that master, but interfusing them with elements of folkloristic starkness and evocative romanticism.

The picturesque elements he was later to develop in the alfresco orchestral Serenades of his later twenties: the delectably bucolic First and the more fugitively personal Second. Meanwhile, the grandeur had already been brought to a head in the tragic First Piano Concerto completed at 25 and comprising a virtual reinvention of the classical concerto on a massive new scale. The chamber works of the period proved scarcely less expansive, notably the First String Sextet with its super-Schubertian saturation of textures and implacably ballad-like variation structure. Not least, having exhaustively explored the piano sonata by 20, Brahms had equally exploited piano variations by 30, culminating in the Handel and Paganini sets, surpassingly learned and brilliant respectively.

Scholars rifling his papers after his imaginary Schubertian death would also have found sketches we now know to have gone into the German Requiem and the First Symphony, and perhaps some of the complete youthful works Brahms was later to destroy. From the motley contrasts of the early pieces so boldly flung together - the old with the new, the heroic with the picturesque, the vernacular with the pedantic - they might have predicted Brahms's evolution into a kind of mid-century Mahler, attempting symphonically to encompass the world. What they, and we, could hardly have foreseen was the true, fundamental development in Brahms's life work from an extrovert to an introverted mode; with the explosive originalities of his earlier music insinuated and developed ever more subtly beneath the apparently resolved surfaces of the later. No doubt, the wounding emotional experiences of his twenties drove him in on himself. But genius can turn even inhibition to account. Scholars are still discovering just how radical Brahms's mature conservativism really was.

Yet, to appreciate his full scope, we need, perhaps, to revalue the early music for its own qualities. The Queen Elizabeth Hall series will include chamber music, songs, and the original nonet version of the First Serenade. A pity that Peter Donohoe, who is running the piano music through, will not be culminating with the Variations and Fugue on a theme of Handel; a pity, too, the South Bank could not run to an orchestral concert for the Serenades and the First Piano Concerto, or a choral programme to encompass such pregnant rarities as the grim Funeral Anthem, Op 13 for chorus and wind band, or the echt-Romantic Op 17 Songs for women's chorus, two horns and harp. For ultimately, the most striking fact, indeed the greatest mystery, about Johannes Brahms was his sudden arrival, as Schumann put it in that famous article, 'springing like Minerva fully armed from the head of Jove'.

Young Brahms, 7.45pm, 30 October, 3, 5, 9, 13 November, QEH (071-928 8800)