How does meantone temperament change the tuning of fifths?

In meantone temperament, the tuning of fifths is intentionally altered to achieve pure, natural major thirds. To accomplish this, fifths are flattened by approximately a quarter of a comma, making them slightly smaller than a natural, perfectly tuned fifth.12

Specifically, the system functions by taking the interval of two octaves and a major third and dividing it into four fifths (C–G–d–a–e′). By tuning these fifths to be flat by a quarter of a comma, the resulting major third (c–e′) becomes perfectly in tune. This adjustment provides a notably pleasing sonority for triads, which are the predominant chord type in this system.12

While this method creates a superior melodic scale with equal whole tones, it results in an uneven distribution of pitch across the keyboard. Because the fifths are tuned to favor specific keys, attempting to play in keys requiring alternative notes—such as using A♭ instead of G♯—creates a severe dissonance known as the "wolf" interval.12