The other day I mentioned Bach’s ‘48’, also known as ‘The Well-Tempered Clavier’: a set, two books of 24 each, (duh) of preludes, each with an associated fugue, for keyboard instruments. So a total of 96 pieces, each of which can stand alone. Why, apart from sheer creative exuberance, of which of course he had plenty, did Bach do this? Was there some special reason? Yes. You see, up to the time of Bach, it was not possible for any one clavier to play decently in all the twenty-four keys — twelve major and twelve minor — possible in western music. If your clavier sounded pretty much in tune in, say, C, it would also be fairly good in the closely related keys of G and F. But if you ventured into, say, A, it began to sound a bit off, and if you had the temerity to try B or D flat it would sound dreadful. Tuners would ask their clients what were their favourite keys, and would tweak their claviers to suit.
But then some ingenious people came up with a way to tune a clavier so that, although no key was absolutely perfect, the ‘offness’ was fairly distributed between the different keys, and only people with very discriminating ears could hear anything wrong, and you could play nicely, on any one instrument so tuned, in all 24 keys. This was a great advance, and Bach celebrated the fact with a set of twenty-four preludes and fugues. Not content with that, he wrote book two, a second complete set. Hence the 48, which has become a standard part of the keyboard repertoire. All pianists aim to reach a level where they can play them all, and many pianists have made complete recordings — the whole 48 will fit onto two CDs, but at the cost of playing some of them at, in my opinion, too high a tempo. I have in my CD collection two complete recordings, both excellent: Keith Jarrett’s, made in 1988, and Angela Hewitt’s, made ten years later.