Which Bach work consists of preludes and fugues exploring equal temperament?

• A. St. Matthew's Passion
• B. The Well-Tempered Clavier
• C. Brandenburg Concertos
• D. Christ lag in Todesbanden

Answer: (B)

The concept being tested is how equal temperament opened up the ability to write and perform preludes and fugues in all keys. Bach’s Well-Tempered Clavier is the collection that demonstrates this idea by presenting 24 preludes and 24 fugues, one pair in each major and minor key, showing how a keyboard piece can modulate through multiple tonal centers within a tuning system that standardizes intervals across the octave. This setup directly illustrates the practical use and musical possibilities of equal temperament on the keyboard.

The other works mentioned are not organized as preludes and fugues exploring temperament. St. Matthew’s Passion is a large sacred vocal work, Brandenburg Concertos are instrumental concertos, and Christ lag in Todesbanden is a chorale-based sacred piece. None of these focus on a complete sequence of preludes and fugues designed to explore equal-tempered tuning in every key, which is why the Well-Tempered Clavier is the correct choice.