Acoustics & Music Theory
why it sounds like that
Concept

Dominant — where it appears

The fifth degree of a key and the major triad built on it, whose leading note and tritone resolve onto the tonic. It is the only degree of the major scale whose triad contains the key's tritone, which is why its function is unambiguous.

Named by 2 essays across 2 fields — each of them below, with the objects they name alongside it.

The triads each scale builds on its own degrees. Every chord that can be stacked in thirds on each degree of each scale, with its quality worked out from the intervals the scale actually supplies. The quality of the chord on each degree is a consequence of each scale's own step pattern rather than of a convention.

What a raised seventh is for

The harmonic minor is usually taught as a scale with an odd gap in it. It is better understood as a repair to a single chord — raising the seventh degree turns the dominant triad from minor to major, and everything else about the scale is the bill for that.

scales · Modes The triad on every degree of every rotation. The quality of the triad built on each degree of each rotation, computed from the set rather than tabulated. The triad on the fifth degree is major in 3 of the 7: Lydian, Ionian, Locrian. Of those, Locrian has no triad on its own first degree to resolve to, and Lydian has its fifth degree on the note the parent collection is built from, so the cadence would confirm the parent rather than the mode. What is left is Ionian — one rotation of the 7, and the others have to end some other way.

One dominant among seven

The triad on the fifth degree is major in three of the seven rotations. One of those three has no triad on its own first degree, and one has its fifth degree on the note the parent collection is built from — so exactly one rotation of the seven has a dominant, and the other six end by moves that cost twice as much in voice leading.

harmony · Modes

Named alongside it

The objects these essays reach for when they reach for this one.

Leading noteCadenceChord qualityHarmonic minorMelodic minorModal harmonyModeTriadVoice-leading

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