Vaughan Williams' Sixth symphony was premiered in 1948, shortly after the end of the Second World War, and is a brilliant but deeply disturbing work of musical art. The musician and scholar Deryck Cooke (who later completed Mahler's Tenth symphony) was at the first performance, and later wrote "The effect was nothing short of cataclysmic - the violence of the opening and the turmoil of the whole first movement; the sinister mutterings of the slow movement, with that almost unbearable passage in which trumpets and drums batter out an ominous rhythm louder and louder and will not leave off; the vociferous uproar of the scherzo and the grotesque triviality of the Trio; and most of all the slow finale, pianissimo throughout, devoid of all warmth and life, a hopeless wandering through a dead world ending literally in nothingness."

Mr. Cooke later wrote a brilliant analysis of the symphony in his book The Language Of Music*. He shows how the symphony is built on four basic terms of musical language - the minor third 1-3-1, the opposition of major thirds and minor thirds, the falling semitone and the conflict between keys separated by a semitone, and the augmented fourth with conflicts between keys separated by that interval. These are four of the most emotionally painful terms of musical language, which goes some way to explaining the impact of this symphony.

The challenge of understanding what this symphony "means" was compounded by the composer's own programme notes for the first performance, which are extraordinary - trivial, flippant and deliberately unhelpful.

All four movements are distinct, but play without a break. The opening allegro begins stormily in F-minor / E-minor, but eventually subsides. A second theme appears on trumpets in close harmony, with an accompaniment sounding like a grotesque Teddy Bears Picnic. A third tune on the strings is more lyrical, but still ambiguously explores the major third I minor third intervals. This theme eventually breaks through into a sunny E major towards the end of the movement, but the F-minor / E-minor tensions of the beginning return at the end.

The second movement is brooding and threatening. It is underpinned by the obsessive rhythm which Deryck Cooke refers to, which alternates with an ominously quiet string chorale passage. Eventually the rhythm drives the whole orchestra to a massive climax, but even this does not bring relief - it is quickly suppressed, and the dark clouds remain.

The scherzo is full of a furious energy, but being based on the intervals of the semitone and augmented fourth, it has great difficulty in achieving anything with this energy. A central section features a sleazy saxophone tune, but this too fails to reach a stable tonality.

Despite several attempts, the movement cannot work up to a proper climax - it just creates a lot of noise which eventually fizzles out.

The closing epilogue is the strangest part of this compulsively strange symphony. It is directed to be played as quietly as possible throughout, with constant reminders to the players not to get any louder, and the content is mere wisps of melody which drift about contrapuntally. The oboe attempts a proper melody, but it fails to achieve any sense of purpose. The movement ends with alternating E-flat I E-minor chords - the desolate E minor having the last word.

So what is this symphony really about? I am reminded of the words of Wilfred Owen in his collected poems, which (I'm sure it's no coincidence) also appeared just after a great World War, in 1920 - ".. all the poet can do today is warn."

*Deryck Cooke: The Language of Music, Oxford University Press, 1959. An attempt to explain how music conveys emotions and meaning. Should be required reading for all thinking musicians.