In 2010 the Canadian academic Susan Wilson unearthed some correspondence in the National Library of Scotland between MacDiarmid and Sorley MacLean, his friend, fellow poet and fellow radical political thinker. In these letters, as late as 1941, it is revealed that MacDiarmid regarded Hitler and the Nazis as potentially more benign rulers than the British government in Westminster.

He was known for his controversial views as a young man. In two articles written in 1923, “Plea for a Scottish Fascism” and “Programme for a Scottish Fascism”, he appeared to support Mussolini’s regime. But the revelation of ambivalent, even pro-Nazi sentiments during WW2 has come as a shock.

These are sobering recollections for Scots, but also for artists generally. Hugh MacDiarmid’s art and his wild, radical, “progressive” idealism can be difficult to disentangle. Artists can be agents of good in society, but we can see that some of them end up supporting evil, blind to the roots and inevitable ends of their thinking.

I wonder what Shostakovich would have made of MacDiarmid’s shenanigans. The Russian’s Fifth Symphony came in the wake of Stalinist purges, the gulags, quotas for punishments against “anti-Soviet” dissidents, millions disappearing, murdered and imprisoned. He could have taught MacDiarmid and the Western fellow-travellers something about utopian fervour and its consequences. He wouldn’t have needed to say a word — the sometimes plangent, sometimes overwhelming blasts of his Fifth Symphony say nothing but imply everything.

There is here a particular modern genius, born in the abyss of political nihilism and despair which produces music that can be heard and understood in different ways. This skill, this facility saved Shostakovich’s skin, but delivered a sarcastic and subtle blow against Marxist totalitarianism. They say that there was a 40-minute standing ovation for this work at its première in Leningrad in 1937. The audience seemed to realise that the music spoke of their pain, tragedy and desolation. Some wept in the slow movement, some said they could feel all the disappeared: they would have known friends and family taken away and murdered by the Communists.

In various 20th-century symphonies we can detect the foreboding of the times — the fear and destruction of war and political oppression. There are some works which, in retrospect, have been regarded as barometers of their era, including a couple performed in this year’s BBC Prom concerts. Elgar’s Second Symphony was written in 1911 and some detect in it the melancholy tread of civilisational collapse. Mahler’s Sixth Symphony was written a few years earlier and is known as his “Tragic” Symphony, full of loss, culminating in literal hammer blows of fate. Furtwängler described this work as “the first nihilistic work in the history of music”. This is a limited analysis of a score which certainly has its fair share of darkness and hopelessness, but also has so much more. The final movement is like a stream of consciousness, astonishingly vast and unusual, with no set sonata pattern or design, strange recapitulations or no recapitulation at all. Like the Berlioz it is hallucinogenic and nightmarish, but it is only at the very end that the music becomes truly despairing.