If one had to choose a symbolic moment when musical Romanticism was born, then the 18 June 1821 would surely be it. That was the day when the 35-year-old Carl Maria von Weber conducted the premiere of his new opera Der Freischütz (The Free shot) at the Berlin Schauspielhaus. This fairy-tale opera about a pact between a huntsman and the devil to achieve a miraculously perfect shot ‘set the German people’s pulse racing’ as a contemporary observer wrote, and it transformed Weber’s reputation at a stroke. Until then he'd been known as a tireless and meticulous opera-house director, first in Breslau and then in Stuttgart, Prague and Dresden, and as a brilliant touring pianist, who’d written some charming songs and glittering show-pieces. But in Freischütz Weber achieved something unprecedented; he expressed the themes and ideals of German Romanticism through a medium where Italian and French models reigned supreme, and where German-language works were regarded as provincial curiosities. No wonder people were amazed, not just in Germany but all over Europe. Beethoven (some 16 years older than Weber and by now regarded as old-fashioned) was merely echoing the opinion of the musical world when he said ‘Weber must now write operas, nothing but operas.’

By the time Weber came to write Freischütz, romanticism had already enjoyed its first bloom in literature and philosophy. During the 1790s, when Weber was growing up, there was a reaction in Germany against dry French rationalism in favour of 'Einfuhlung – ‘feeling into’. Imaginative sympathy with the particular spirit of a nation or people was now regarded as the real path to wisdom. The earliest literary manifestations of this new spirit were Ludwig Tieck's folk-tale collections of 1797. Tieck was a powerful influence on the young Weber, as was the chief philosopher of Romantic nature mysticism, FW Schelling.

The favourite themes of these early romantic writers would become Weber's 20 years later. Among these were an idealising view of the past, peopled by medieval knights, a fascination with the ‘exotic’ East, and a taste for the supernatural, very similar to that of the English Gothic novelists. Arching over these was the idea of Nature as a vast and mysterious realm beyond men’s understanding, and a reverence for the people who lived closest to it, i.e. the ‘folk’. So it might be predicted that Weber would show an interest in folk-song – and in fact he did collect folk songs, and used them in his own music. Among his songs are several settings of poems from Des Knaben Wunderhorn, the folk-song collection that inspired Mahler some 60 years later. And the theatre too was in his blood. His childhood years were spent travelling around Germany with his father’s troupe of strolling players.

But what of the music itself? What makes it sound romantic? There's a moment early in the overture to Freischütz that epitomises the newspirit that so electrified those early audiences. After a busily active passage, the music suddenly settles on a tremolando chord, through which the horns sound. Above this glowing texture the clarinet plays a plaintive descending line, which rises and then descends to a sighing close. All the hallmarks of romanticism are there; the yearning melody, with its constant sighing apoggiaturas: the sudden disappearance of the pulse, leaving only a mysterious whispering in the strings; and the sudden irruption of the horns, which transports us instantly to the mysterious Teutonic forest.

All this might remind one of Wagner – but Weber's romanticism was of a very different kind, more akin to the universal, supra-national idealism of Schiller – an idea thrillingly expressed by Beethoven in his Ninth Symphony (premiered in 1824, the year after Weber's opera Euryanthe). He was not an out-and-out nationalist, despite his love of German folk-song, and his determination to create a new and specifically German opera was tempered by the knowledge that Germany had much to learn from other musical cultures.

He once said ‘I am in favour of quality, wherever it comes from’, and was not afraid to go against the craze for Italian opera by programming the new 'revolutionary' operas of Gossec and Méhul. Weber learned from these composers himself; in Freischütz he grafted their orchestral effects and striking harmony onto to the essentially German form of the ‘Singspiel’ or ‘sung play’. In his last opera Oberon he made use of some oriental dances he discovered, something Wagner would never have countenanced.

But the main difference is that Weber’s form of romanticism is much closer to the classical style of Haydn and Mozart, which reached its final perfection during Weber’s youth and early manhood. Although young Weber may have imbibed the romantic spirit from the tales of Hoffman and Brentano, his musical training was thoroughly classical – a striking example of how music lagged behind the other arts in adopting the new aesthetic. And if we're tempted to think of Weber as a thorough-going romantic, we should remember that he passed the whole of his life in a working environment not very different from Haydn’s.

From his 18 year onwards, he was continuously in service as a Kapellmeister, or master of music, at one of the German princely courts (apart from a spell at a private opera house in Prague). The contrast with Beethoven, who never held a position at a court and lived an often precarious life as a freelance, is striking. Musically, there is a clarity of phrase and harmony which links him with the previous generation. We should not look, in Weber, for the kind of ‘endless melody’, chromatic harmony and massive blended orchestration we find in Wagner, born 27 years later.

Useful though the experience of being a kapellmeister was from a practical point of view, there's no doubt it exacted a terrible toll on Weber’s always fragile health. He had been born with lame foot, and from his early 20s showed signs of tuberculosis. But he made up for it with boundless energy, and a quiet determination that would occasionally explode in temper.

His letters are full of pathetic laments about the gruelling round of official duties, which included ‘organising all the contracts, new regulations for orchestra and chorus, bringing a muddled library into order, as well as being overrun by hordes of people – it’s indescribable... I get up at six and often work through until midnight.’ From 1817 onwards he had at least had the comfort of a happy domestic menage, after he married Caroline Brandt, a soprano in the opera company in Prague. Weber's chief responsibility lay in the opera house, where his efforts to bring in new non-Italian repertoire and to reform working practices met with sullen resistance. In Dresden, his last appointment, Weber had to contend with a rival Royal Kapellmeister who did everything in his power to frustrate his plans.

Yet the amazing thing is how far this ‘poor week little mannikin’ (as Beethoven rather unkindly described him) succeeded in his aims, despite his tragically short life (Beethoven actually outlived Weber by about nine months.) Of all Weber's innovations, perhaps his most spectacular and talked-about reform was his elevation of the role of orchestral conductor. Previously he had been a discreet timekeeper, seated in the middled of the orchestra at the keyboard; Weber turned him into a fully-fledged interpreter who could control both player and singers from his commanding position at the front. This made him the ancestor of the conductor-as-hero personified later in the century by Berlioz, Mahler.

It wasn't only as a conductor that Weber drew amazed admiration all over Europe. He was also one of the great virtuoso pianists of the day, on a par with Hummel, Czerny and Kalkbrenner, and like them he wrote a number of brilliant showpieces and concertos to play on his concert tours.

But he was suspicious of what he called ‘these damned piano fingers, which through endless practising become the tyrants and despots of creation,’ and in his reviews of other pianists always praised a singing tone over mere dexterity. In fact the antithesis is a false one, as Weber's own piano works show. Given that the piano is,as Debussy said, only a box of strings and hammers, the piano cannot ‘sing’ at all; but one way of creating an illusion of a singing tone is to decorate the melodic line with swathes of trill, scales, and chromatic neighbouring notes. Weber was a master of this kind of expressive brilliance, and there are times when he foreshadows Chopin and Liszt.

One unavoidable fact about pianistic brilliance, whether expressive or merely impressive, is that it takes time. Like arabesque, it needs a relaxed frame to spread its tendrils. (This is why one finds little ‘brilliance’ in the classical sonatas of Haydn and Beethoven, where everything is stated in the most concise way possible so as to maximise the sense of dramatic contrast). Such a frame was best provided by the genre of ‘character piece’, of which there are plenty in Weber.

Titles like ‘Momento Grazioso’, ‘Invitation to the Dance’, and ‘Shepherd’s lament’ (from the Trio) tell us to expect this kind of rhapsodic, decorative melody. What lifts Weber’s above the common run of such genre pieces is the distinction of the melodic line, and what one might call its emotional mobility – the way it can turn in a moment from pliant grace to supplication to passionate assertion.

However, like other composers born under Beethoven's shadow, Weber felt an obligation to go beyond the the character piece, and write proper sonatas. Whereas some composers were intimidated by the prospect, and tried to squeeze a relaxed romantic style into a severe Beethovenian form, Weber adapted the sonata to his own purposes. There is a steady progression from the extrovert display of the first sonata (whose opening downward rush of semiquavers Chopin recalled in his ‘Revolutionary’ Study, written some 15 years after Weber’s death) to the more disciplined and introverted No. 4, written the year after the Freischütz premiere.

Weber used the idea of a programme on several occasions, most famously in his solo piano piece Invitation to the Dance. The diffident opening describes the dancer approaching a lady at a ball. He then bears her off into a brilliant waltz, which rises to a pitch of excitement until he takes leave of her, when the opening mood returns. Just before that happens, though, there is a mysterious moment which saves the piece from complete predictability.

The waltz rhythm continues, but the music moves suddenly to a remote key, and becomes unexpectedly hushed. The effect is like a memory; it's as if we've already left the dance and are looking regretfully back at it. This evocation of the power of the memory links Weber to later romantics, particularly Schumann. The effect of distance produced by these sudden modulations needn’t be a distance of memory; it could be the mysterious distances of a haunted place, as in the famous Wolf Glen’s scene from Freischütz. Or it could be the general sense of things coming ‘from afar’, as in the scene in Freischütz where the chorus of Bridesmaids moves off stage in mid-song, so that their disembodied voices are heard from off-stage.

These devices lend a feeling of ‘enchantment’ to a musical or dramatic scene, which was always Weber’s chief aim. More powerful than any of them was the use of new orchestral colours. Here Weber managed to be both a pioneer and a master – all his novel effects actually ‘come off’ in practice, thanks in part to his long experience as a conductor. Some of the most striking are in Freischütz. Here Weber says he wanted to portray the sinister element with ‘the lowest register of the violins, violas and basses, particularly the lowest register of the clarinet... then the mournful sound of the bassoon, the lowest notes of the horn, the hollow roll of drums...’

All this Weber had achived by the time of that famous Freischütz premiere. Yet everything he had written until then could be called an early work. The opera that followed Freischütz, Euryanthe, is in every way more mature. Not until Wagner’s Lohengrin was its adventurous harmony surpassed. By this time Weber’s reputation was Europe-wide, and he received a commission from Covent Garden for a new opera, Oberon. But his health was shattered, and Weber’s letters show a foreboding of his own end. ‘Whether I go to London or not, in a year I'm a dead man. But if I go, my children will eat when their father's dead, and I stay they’ll starve.’ On 5 June, two months after the premiere of Oberon he died in London, and was buried in Moorfields. Eighteen years later his successor in Dresden, Richard Wagner, arranged for his remains to be reburied in Germany. At his grave, Wagner made a speech in which he said ‘the Briton does you justice, the Frenchman admires you... but only the German can love you’. Fortunately the last 150 years have proved him wrong.