Was Bach’s Well-Tempered Clavier Written for Equal Temperament?

The Chinese title commonly given to Das Wohltemperierte Klavier can suggest that Bach was demonstrating modern twelve-tone equal temperament. More precisely, wohltemperiert means “well-tempered”: a keyboard could be played in every major and minor key without retuning, and remote keys no longer produced intolerable intervals.

That does not necessarily mean dividing the octave into twelve exactly equal semitones. Bach’s period knew several unequal “circulating” temperaments. They distributed the tuning discrepancy so that every key remained usable, while preserving small differences in interval size and tonal colour. Book I moves through twenty-four preludes and fugues in all twelve major and twelve minor keys. It demonstrates that the keyboard can travel through the full tonal system; it is not a written specification for one tuning.

The temperament Bach actually used remains disputed. Some scholars have derived schemes from the decorative loops on the 1722 manuscript’s title page, while others regard that evidence as insufficient. Claims that any one reconstruction is Bach’s uniquely correct system therefore go beyond what the surviving evidence can establish.

Performing the work on a modern equal-tempered piano is entirely legitimate, but recordings in historical temperaments can sharpen the ear. Listen for whether C major and C-sharp major seem merely transposed, or whether their chords also acquire subtly different tensions and colours. The point is not to choose a camp. It is to hear tuning as part of musical structure: Bach made every key habitable, without necessarily giving every room exactly the same light.

https://www.bach-digital.de/receive/BachDigitalWork_work_00011162
https://www.tandfonline.com/doi/abs/10.1080/09298215.2024.2375552