Just Intonation

In music, just intonation is any musical tuning in which the frequencies of notes are related by ratios of whole numbers. Any interval tuned in this way is called a just interval; in other words, the two notes are members of the same harmonic series.Justly tuned intervals are usually written either as ratios, with a colon (for example, 3:2), or as fractions, with a slash (3/2). Sometimes a technical distinction is made between the two styles, but in general they are equivalent and interchangeable. Although in theory two notes tuned in an arbitrary frequency ratio such as 1024:927 might be said to be justly tuned, in practice only ratios using quite small numbers tend to be called just; more complex ratios are often considered to be rational intonation but not necessarily just intonation. Intervals used are then capable of being more consonant.
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