meantone

Meantone is a family of historical musical temperaments used in Renaissance and Baroque keyboard practice. Its defining idea is to temper the syntonic comma out of the tuning by narrowing the fifths, which makes the major thirds sound much closer to their just intonation. In practice, fifths are tuned slightly flatter than a perfect fifth, producing a harmony that is unusually consonant for thirds compared with later equal temperaments.

The most common form is quarter-comma meantone, in which each fifth is adjusted by one quarter of the syntonic comma. This yields major thirds that are very close to the just ratio 5:4, giving a bright, singing quality to chords. However, because the same fixed size of fifth must be used across the keyboard, some keys become problematic, producing a wolf interval that severely compromises those keys. As a consequence, the number of usable keys in quarter-comma meantone is limited, especially for distant modulations.

Historically, meantone was influential from the late 16th century through the 17th and into the early 18th century, particularly in Europe for organ, harpsichord, and lute music. By the mid-18th century, well-tempered and then equal-tempered systems began to supplant meantone to allow more keys in modulation. In modern practice, meantone is revived by performers of early music and by keyboard builders aiming to recreate the historical sound, especially in repertoire that emphasizes bright, pure-sounding thirds.