and the organ (which operates using air instead of strings), but not the regal and the then newly-invented pianoforte.

The modern German spelling for the collection is Das wohltemperierte Klavier (WTK; ). Bach gave the title Das Wohltemperirte Clavier to a book of preludes and fugues in all 24 keys, major and minor, dated 1722, composed "for the profit and use of musical youth desirous of learning, and especially