Acoustics & Music Theory
why it sounds like that
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Scales and modes

Which seven of the twelve, and what changes when the same seven start somewhere else.
CC♯DE♭EFF♯GA♭AB♭B2 · 2 · 1 · 2 · 2 · 2 · 1steps, in semitonesthe short chords are the semitones — two of them, unevenly spaced

Seven of the twelve, chosen unevenly

A major scale is a selection of seven positions out of twelve, and the selection is lopsided on purpose. The two semitones sit where they do because an even choice would destroy the thing that makes a scale usable.

 CC♯DE♭EFF♯GA♭AB♭BCLydianIonianMixolydianDorianAeolianPhrygianLocrianbrightest at the top, darkest at the bottomeach row drops exactly one note by a semitone from the row above

The same seven, started later

A mode is not a new scale. It is the same seven notes with a different one treated as home, and the entire change in character comes from reassigning which degree the semitones fall next to.

 CaGeDbAf♯Ec♯Ba♭F♯e♭C♯b♭A♭fE♭cB♭gFdone step= one fifth= one sharpouter ring: major keys · inner ring: their relative minors

Keys are neighbours, and the map is computed

Two keys a fifth apart share six of their seven notes. That single fact generates the circle of fifths, the key signatures, the shape of nearly every modulation, and the sense that some keys are far away.

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