In music, just intonation (sometimes abbreviated as JI) or pure intonation is any musical tuning in which the frequencies of notes are related by ratios of small whole numbers. Any interval tuned in this way is called a pure or just interval. Pure intervals are important in music because they naturally tend to be perceived by humans as "consonant": pleasing or satisfying. Intervals not satisfying this criterion, conversely, tend to be perceived as unpleasant or as creating dissatisfaction or tension. The two notes in any just interval are members of the same harmonic series. Frequency ratios involving large integers such as 1024:729 are not generally said to be justly tuned. "Just intonation is the tuning system of the later ancient Greek modes as codified by Ptolemy; it was the aesthetic ideal of the Renaissance theorists; and it is the tuning practice of a great many musical cultures worldwide, both ancient and modern."