Chopin, the D-flat Prelude (1839).

HOPE
Equal temperament carried the day, carried the century. We all grew up hearing it (though of course we didn’t know it). All our ears were conditioned, thoroughly conditioned, to perceive equal temperament music as the way music not only should be but simply IS.

We bulldozed a rocky aural landscape and made it smooth, plain, simple. Music, even the great music, became in a sense "lite" music. Beethoven as fast-food.

All was not lost. Lurking about as always were a few mavericks, music historians, highly skilled piano technicians, even a few musicians, who were aware of what had happened and who objected strenuously.

Think of them as sort of musical tree-huggers, a tiny minority who watched helplessly as the great, diverse sonic forests were leveled. They protested and for a long time no one paid any attention.

A bland simple diet goes only so far.

As the century continued, performers and audiences slowly began to want more: real aural nourishment. The "performance practices" movement appeared whose goal was to play music as it had been played when originally composed. This meant reviving old instruments, old techniques of playing those instruments, and finally old methods of tuning those instruments.

Aha!