Oliver Kamm was on Today this morning discussing the newly published diaries of Prokofiev. His basic point was that a piece of music is just that, a piece written in the language of music, and any diaries or biographical notes are irrelevant to it.

I take his point. We don't need to know if Prokofiev preferred apples to pears or whether he enjoyed football, but biographical information can be essential to a full understanding of some works or composers. What about, for example, Shostakovich? Of course his works can be enjoyed on their own terms, but I would contend that one can’t understand them – or what he intended them to be – without knowing at the very least their background, if not his own circumstances. Take the Fifth Symphony. It lends itself, in the fourth movement, to a garishly triumphant performance. Even the title he gives would support such a reading: "a Soviet artist's response to just criticism".

And yet. Even without the evidence of Testimony, Solomon Volkov's much-challenged book (he claimed they were Shostakovich's memoirs as dictated to him), it is clear from all the biographical and historical evidence that the piece was meant as anything but a glorification of Soviet communism. To hear it performed properly with all the tragic irony of the final movement, surely it is not only the performers who need to know the background; so, too, does the audience. The same - even more obviously, I would argue - applies to his 'Leningrad Symphony'.

It's a longstanding and fascinating debate.