 In systems other than equal temperament, however, there is often a difference in tuning between intervals that are enharmonically equivalent.In tuning systems that are based on a cycle of fifths, such as Pythagorean tuning and meantone temperament, these alternatives are labelled as "diatonic" or "chromatic" intervals.Under these systems the cycle of fifths is not circular in the sense that a pitch at one end of the cycle (e.g., G) is not tuned the same as the enharmonic equivalent at its other end (A); they are different by an amount known as a "comma".