Tom Service explores JS Bach's extraordinary The Well-Tempered Clavier, a series of 48 preludes and fugues for keyboard in all 24 major and minor keys. It's widely regarded as a towering achievement and a cornerstone of western art music. The 19th century German conductor and pianist, Hans von Bülow famously described it as “The Old Testament of Music” and generations of musicians and scholars have spoken of its monumental stature in the history and development of music. From the first, C major prelude with its lean and simple series of arpeggios, taking listeners on an exquisite harmonic journey, through to darker and more complex moments, with plenty of playfulness and joy along the way, The Well-Tempered Clavier is an astonishing feat of imagination. These two books of preludes and fugues are a treasure trove, where Bach combines contrapuntal wizardry with his extraordinary gift for expressing human emotion. With help from American pianist, Jeremy Denk, Tom Service lifts the lid on The Well-Tempered Clavier to discover its secrets. Producer: Jonathan Hallewell