4:5:6

Chord information

Harmonics	4:5:6
Subharmonics	1/(15:12:10)
Intervals from root	1/1–5/4–3/2
Cents from root	0¢–386¢–702¢
Step intervals	5/4, 6/5
Step cents	386¢, 316¢
Color name	yo or y
Prime limit	5
Genus	3⋅5 (15)
Intervallic odd limit	5
Otonal odd limit	5
Utonal odd limit	15
Consistent edos (d ≥ 2)	3edo*, 12edo*, 15edo*, 19edo**, …
* 2 ≤ d < 4; ** 4 ≤ d < 8; *** 8 ≤ d < 16; …

4:5:6 is the classical major triad, and can also be referred to as the Ptolemaic major triad. It is found on the I (1⁄1), IV (4⁄3), and V (3⁄2) of Ptolemy's intense diatonic scale (Zarlino), which is perhaps the most common 5-limit diatonic.

However, there are other 5-limit diatonic scales which don't have the Ptolemaic major triad occurring in all the same places. For instance, Aura is known to use a diatonic major scale in which this chord only occurs on the I and V scale degrees while using a Pythagorean major triad (that is, 64:81:96) on the IV. Conversely, in the diatonic minor scale that Aura uses, this chord only really appears on the bVI. Compared to its Pythagorean counterpart, the Ptolemaic major triad sounds like it's more easily tonicized, a fact which Aura exploits in order to help stabilize Ionian mode in fixed pitch diatonic scales. Because of these properties, the Ptolemaic major triad has earned its status as a bread-and-butter chord in 5-limit harmony.

There are a number of possible tetrads which can be reasonably built off of this triad, such as 36:45:54:64 and 20:25:30:36 in the 5-limit, as well as 4:5:6:7 in the 7-limit and 32:40:48:55 in the 11-limit.