A scale is a sequence of notes arranged in ascending or descending order that forms the melodic and harmonic foundation of a piece. The most fundamental scale in Western music is the major scale, which follows the interval pattern whole-whole-half-whole-whole-whole-half. The C major scale, consisting of C, D, E, F, G, A, B, contains no sharps or flats and is the simplest major scale to play on the piano because it uses only the white keys. Every major scale follows the same intervallic structure, just starting on different pitches and incorporating different accidentals.
Minor scales come in three principal forms, each with a distinct character. The natural minor scale follows the pattern whole-half-whole-whole-half-whole-whole, which produces a darker, more melancholic sound compared to the major scale because it lowers the third, sixth, and seventh scale degrees. The harmonic minor scale raises the seventh degree of the natural minor by a half step; this creates an augmented second interval between the sixth and seventh degrees and provides a leading tone that pulls strongly toward the tonic. The melodic minor scale further raises the sixth degree along with the seventh when ascending, eliminating the augmented second; in classical practice, it reverts to the natural minor when descending.
Beyond seven-note scales, the pentatonic scale uses only five notes per octave. The major pentatonic consists of scale degrees 1, 2, 3, 5, and 6 of the major scale, following the interval pattern whole-whole-minor third-whole-minor third. The minor pentatonic uses 1, ♭3, 4, 5, and ♭7, and is one of the most widely used scales in rock, blues, and pop guitar. The A minor pentatonic, for example, contains A, C, D, E, G. The blues scale is a minor pentatonic with an added ♭5 blue note, creating a chromatic passing tone that gives blues music its characteristic sound. Other specialized scales include the whole tone scale, consisting of six notes each a whole step apart with a dreamy and ambiguous quality, and the chromatic scale, which includes all twelve pitches within an octave, each a half step apart.
The seven diatonic modes offer additional tonal colors by starting the major scale on each of its seven scale degrees. The Ionian mode, beginning on the first degree, is identical to the major scale, while the Aeolian mode, beginning on the sixth degree, is identical to the natural minor scale. Between them lie the Dorian mode, with a raised sixth giving it a slightly brighter, jazzy quality; the Phrygian mode, with a distinctive half step between the first and second degrees evoking Spanish or Middle Eastern flavors; the Lydian mode, with a raised fourth degree producing a dreamy, floating character; the Mixolydian mode, which is a major scale with a lowered seventh forming the basis of dominant seventh chords; and the Locrian mode, whose diminished fifth above the tonic makes it the most unstable mode and rarely used as a tonal center.