Hans von Bulow called Bach's Well Tempered Clavier 'The Old Testament' of music -- Beethoven's 32 piano sonatas being the so called 'New Testament. Bach's set of 48 preludes and matching fugues is the ultimate in keyboard instruction. Intended for his son Wilhelm Friedemann, they consist of one prelude and fugue in each of the twelve major and minor keys, arranged in chromatic order. Bach used not only the '48' for teaching purposes, but also his French and English Suites as well. According to one of his pupils, Bach would set them to work on the Inventions first, followed by the Suites, and if the great man didn't feel like teaching, he'd sit at the keyboard and play from the preludes and fugues 'and thus turned these hours into minutes' according to pupil Heinrich Nikolaus Gerber. These works became the essential study for all the great pianists -- starting with Bach's sons, through Mozart, Beethoven, Hummel, Mendelssohn, Chopin, Schumann, Brahms, Liszt, Rachmaninov, Prokofiev and all the pupils of these great composer pianists.
Daniel Barenboim has said of the '48' 'The chromatiscism in the C sharp minor prelude from Book 1 brings Wagner's Tristan und Isolde to mind. Or the fugue in E flat, which could be straight out of a symphony by Bruckner. In other words, The Well Tempered Clavier is not only the sum of everything that has preceded it, but it also points the way ahead. In European music there are very few composers whose work that applies. This is one of the main reasons for the towering stature of Bach's music.'

Further information
- Recording made in 2008
- Harpsichords by Bruce Kennedy after Mietke (Book 1) and by Cornelius Bom after Ruckers (Book 2)
- Pieter-Jan Belder studied with Bob van Asperen at the Amsterdam Sweelinck Conservatorium. He has worked with Franz Bruggen, Ton Koopman, Philippe Herreweghe and Rene Jacobs. He has recorded 10 CDs as part of Brilliant Classics' Bach Edition, and has recorded all the Scarlatti sonatas. He is currently working on the complete recordings of keyboard music by Soler and Rameau
- Comprehensive booklet essay