The Well-Tempered Clavier (also known as WTC, BWV 846–893) is the title of two collections of musical works for solo keyboard instruments by the Baroque composer Johann Sebastian Bach. The first collection was written in 1722 and the second was written in 1742, but they were not published until 1801, fifty years after Bach died. Although the music was written for the harpsichord, which was popular at the time, today it is usually played and heard on a piano.