There are sad keys and glad keys, so they say; F sharp minor is turbulent and C major is sunny. Every pianist knows how a key feels under their fingers, as every key has its own combination of black and white on the keyboard. Before the Baroque period, keyboards had to be re-tuned to play in each different key. But with the development of the modern piano, so-called “equal temperament” evened out the differences between the keys. One great masterpiece represents this development – JS Bach’s The Well-Tempered Clavier, which expresses his faith in the new tuning system by having pieces in all the 24 different major and minor keys. But another curious factor of keys still remains a problem – the fact that different countries tune their pianos to different pitches. So middle C is, for instance, a bit higher in Germany than in the UK. Featuring Pierre-Laurent Aimard, Iain Burnside and David Owen Norris.