Diatonic Scale
A seven-note scale that moves from a root tone to its octave in a fixed pattern of whole and half steps.
What it means
A diatonic scale consists of seven notes arranged within an octave in a fixed sequence of five whole steps and two half steps. The name comes from the Greek diatonikos, "proceeding through the whole tones," and distinguishes this type of scale from the chromatic scale (twelve half steps) and the pentatonic scale (five notes).
Where the two half steps fall within the seven-note row determines the scale's character. In the major scale they lie between the third and fourth degrees and between the seventh and eighth; in the natural minor scale, between the second and third and between the fifth and sixth. The old church modes are also diatonic rows, just with the half steps in different places.
In the notation
A diatonic scale occupies seven consecutive lines and spaces on the staff without skipping any letter name; each note name appears exactly once. The key signature fixes which notes are raised or lowered by sharps or flats to produce the scale's characteristic half-step pattern.
Musical use
The major scale and the three forms of the minor scale (natural, harmonic, melodic) form the tonal backbone of Western music since the seventeenth century. The seven medieval and Renaissance church modes are diatonic too; they differ from major and minor only in where the half steps fall.
The diatonic scale should be distinguished from the chromatic scale, which moves through all twelve half steps of the octave evenly, and from the whole-tone scale, made up entirely of whole steps. The pentatonic scale, a five-note row, is also distinct, though many pentatonic scales can be understood as a selection from a diatonic row.
Functional harmony's entire system of scale degrees rests on diatonic order: each degree receives a fixed function (tonic, subdominant, dominant, and so on) because its distance to its neighbors is fixed by the scale's half-step pattern.
Performance practice
Practice diatonic scales first in major and natural minor to fix the characteristic placement of the half steps in your fingers or ear. When singing, pay particular attention to the narrow half steps between the third and fourth and the seventh and eighth degrees in major, since they are easily sung too wide.