Three portraits of Beethoven, in 1803, 1815 and 1820

If Beethoven is among the very few composers to be associated with particular keys, it’s largely because he lived at a time when technological advancements in instrument design had made the performance of music in any given tonality possible, and before the first signs of this system breaking down – heralded by the ambiguous tonalities of Wagner’s Tristan and Isolde, not even four decades of Beethoven’s death.

For much of the Baroque and Classical periods, composers were limited by the physical capabilities of instruments. This was most obviously the case whenever brass instruments were included: the trumpet sounded at its most brilliant in D major, so this was the key chosen by Handel for (to cite one example among many) the bass aria ‘The trumpet shall sound’ from Messiah, as well as Bach in several sections of his Mass in B minor. Even instruments in the strings family – the foundation of the orchestra – tended to favour keys centred around the notes to which their strings were tuned, being much easier to play in.

Mozart is arguably the only composer before Beethoven for whom there was a clear association between some keys and a particular mood, especially with regards to minor keys. G minor – his key of choice for two symphonies, five chamber works and perhaps most notably, Pamina’s despairing ‘Ach, ich fühl’s’ in The Magic Flute – is introspective in his hands, sometimes unsure of itself and prone to outbursts of high emotion.

The tragic undertones are even clearer in his music in D minor. Whether it’s in the Requiem Mass or an unexpectedly dramatic Fantasia for solo piano, it can be as implacable as the stone statue it represents in Don Giovanni (by some distance the darkest of his operas). By contrast, he can come across as rather severe in C minor, with works including the Great Mass, one of his most notable Serenades for wind instruments … and a late piano concerto (No 24) particularly admired by one Ludwig van Beethoven.

To say the younger composer embraced this same tonality would be putting it mildly. It’s there in his first published works, as the last of a set of three piano trios dated 1795, followed by two piano sonatas in 1798, one of these being the Pathétique. We won’t name all the others here, but those worth highlighting are his Piano Concerto No 3 – the centrepiece of our Yeol Eum Son plays Beethoven concerts (8-9 May) – the funeral march that forms the second movement of his Symphony No 3, Eroica, a set of 32 Variations on an Original Theme for solo piano, the seismic Symphony No 5 and the last of his 32 piano sonatas.

Following Mozart’s lead, there’s a definite serious-mindedness to these works, but with an added spirit of defiance. There’s invariably a sense of Beethoven grabbing something by the scruff of the neck and refusing to let go until it has listened to what he has to say. This may be anything from the individual listener to the world at large – not forgetting the performers themselves, on whom he places strenuous demands – but either way, the music is forceful and almost relentless in its drive, even when it moves away from C minor.

Take the moment in the first movement of his Symphony No 5 when Beethoven shifts unexpectedly into C major, a move which (in anyone else’s hands) would bring about a degree of relaxation. Not so here: there’s been so much tension in the music that this about-turn comes across as ominous, the prelude to something far worse - and so it proves to be. It’s not long before the prevailing C minor reestablishes itself with a vengeance, sweeping away all before it, its power unabated.

The restless drive of this C minor mood goes all the way back to that early Piano Trio, and would become one of the composer’s defining characteristics, but especially when he writes in this key. By contrast, the slow movements of these works tend to be havens of tranquillity, a refuge from otherwise stormy emotions. It’s certainly the case in the Pathétique, whose Adagio cantabile ranks among the best-known of Beethoven’s compositions.

It's worth mentioning some naysayers among the critics, for whom Beethoven’s earlier C minor works smack of unoriginality, the composer coming across (as Joseph Kerman put it) as “an unknowing prisoner of some conventional image of passion, rather than his own passion’s master.” However you look at it, it’s a decidedly unkind view: no composer, not even Beethoven, can really be expected to have written absolute masterpieces from the word go, and given his angry young man tendencies at the time, there’s surely something to be admired in such restraint. The frequency with which he turned to C minor in his younger days suggests something about the key resonated with him, so it is hardly surprising that he explored its possibilities at some length, and that his true masterpieces in C minor did not emerge immediately.

In these later works, it could be argued that what Beethoven does after establishing a defiant mood in their first movements is even more telling. Going back to the Fifth Symphony, its opening movement is so ubiquitous that the others tend to get overshadowed, a great pity considering the transition from the third into the finale. After a ghostly recasting of the Scherzo’s main theme – on quiet plucked strings, with little flutters from the woodwind – everything comes to rest on a single held chord under which the timpani beats out an ominously quiet rhythm. The violins pick out the movement’s main theme again, as if trying to find a way out of this impasse, and just as you think they might be going round in circle, the tiniest chink of light appears. It expands slowly, the violins’ melody rises and gains in confidence, and the shackles are finally cast off as the entire orchestra erupts in a blaze of triumph as the finale gets underway, in a gloriously optimistic C major.

The last piano sonata takes a very different approach. After a first movement that is as stormy as you’d expect, only ending (unexpectedly) in C major, Beethoven sticks to this key for the second movement, a slow theme and variations. It last almost twice as long as the first, and establishes such an expansive, transcendental calm that there is no need for a third: the conflict has melted away, and Beethoven achieves such delicacy in this music that it is tantamount to a vision of the eternal.

Where does the C minor piano concerto fit in? The opening can seem a little four-square – it can’t compare with the equivalent passage in Mozart’s, a mysterious sinew which slithers through all manner of unlikely keys before somehow finding its way home – but Beethoven works wonders with his fanfare motif. Its closing heartbeat rhythm even pre-empts the four-note figure that propels the Fifth Symphony, insinuating its way into much of the first movement and playing a vital role in the drive of the music.

The slow movement takes us in the remote key E major, far from the turbulent emotions, for some exquisitely lyrical music – before the finale re-establishes a more agitated mood, though this time the sun does occasionally peek out from behind the dark clouds. That said, it’s less a case of C minor being vanquished as a playful C major eventually prevailing: although he was making some headway in establishing himself as a composer at the time, Beethoven was enough of a showman to appreciate the importance of leaving his audience with a smile on their faces.