On the page they look like nothing. ‘Ruins’, Schumann called Chopin’s twenty-four Preludes. Some are so short, so superficially easy, that they’ve become a staple of ‘Classics for Beginners’ books. It took me years to realise how great these pieces were, so effectively had I butchered them as a child, turning the most delicate ones into odes to teenage angst. With a bit of distance, however, and a good performance, their genius suddenly hits you, as in Cortot’s feverish recordings. In the Frenchman’s hands, mawkish scraps became vivid Polaroids.