Few music historians agree as to just how Bach came to write his two concertos for three pianosa complicated, not to say cumbersome, kind of composition on the face of it. Bach Biographer Albert Schweitzer cites a tradition that Bach wrote them (actually for the light-toned clavier) to play with his two eldest sons, Wilhelm Friedemann and Carl Philipp Emanuel. Others believe he wrote them for his students while he was conductor of the Collegium Musicum in Leipzig.
Whatever the original idea, the grace and contrapuntal vigor of the concertos have delighted musicians ever since. Some famous performances: Chopin, playing with Liszt...