4/3

Interval information

Ratio	4/3
Factorization	22 × 3-1
Monzo	[2 -1⟩
Size in cents	498.045 ¢
Name	just perfect fourth
Color name	w4, wa 4th
FJS name	[math]\displaystyle{ \text{P4} }[/math]
Special properties	square superparticular, reduced, reduced subharmonic
Tenney norm (log2 nd)	3.58496
Weil norm (log2 max(n, d))	4
Wilson norm (sopfr(nd))	7
[sound info]
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4/3 is the frequency ratio of the just perfect fourth. Its inversion is the perfect fifth, 3/2. In the florid organum of Medieval music, 4/3 was reliably considered a consonance, and indeed was frequently emphasized. Once major thirds with a tuning approximating 5/4 began to be treated as consonances, however, the perception of 4/3 was altered to where it was at times considered a dissonance.

In Aura's music theory, which is in some respects derived from both florid organum and the practices of later counterpoint, it should be noted that the traditional 1/1-4/3-3/2 suspension is considered a dissonance purely because of the presence of the 9/8 interval between the 4/3 and the 3/2, and likewise, a 1/1-4/3-16/9 quartal chord is also considered a dissonance because of the 16/9 interval between the notes on the outside of the chord.

See also

• 3/2 – its octave complement
• 9/8 – its fifth complement
• Fourth complement
• Gallery of just intervals
• Wikipedia: Perfect fourth