Music.

Music scale.

Scale is any set of musical notes ordered by fundamental frequency or pitch.

Scale ordered by increasing pitch is an ascending scale, and a scale ordered by decreasing pitch is a descending scale.

The distance between two successive notes in a scale is called a scale step.

For Western music with 12 tones in octave used several definition of steps:

• semitone, half step is 2^(1/12)
• whole step, whole tone, major second is 2^(2/12)

Chromatic scale is a musical scale with twelve pitches, each a semitone above or below another. On a modern piano or other equal-tempered instrument, all the semitones have the same size (100 cents). In other words, the notes of an equal-tempered chromatic scale are equally spaced.

• https://en.wikipedia.org/wiki/Chromatic_scale

Diatonic scale (or heptatonia prima) is a scale composed of seven distinct pitch classes: 2–2–1–2–2–2–1.

• https://en.wikipedia.org/wiki/Diatonic_scale

Minor scale: 2-1-2-2-1-2-2.

• https://en.wikipedia.org/wiki/Minor_scale

Pentatonic major scale: 1, 2, 3, 5, 6. Pentatonic minor scale: 1, ♭3, 4, 5, ♭7.

• https://en.wikipedia.org/wiki/Pentatonic_scale

The eight degrees of the diatonic scale are also known by traditional names:

• 1st degree – Tonic (key note)
• 2nd degree – Supertonic
• 3rd degree – Mediant
• 4th degree – Subdominant
• 5th degree – Dominant
• 6th degree – Submediant
• 7th degree – Leading tone
• 8th degree – Tonic (Octave)

Intervals names:

• Minor second - 1 semitones.
• Major second - 2 semitones.
• Minor third - 3 semitones.
• Major third - 4 semitones.
• Perfect fourth - 5 semitones, 4:3.
• Perfect fifth - 7 semitones, 3:2.
• Minor sixth - 8 semitones.
• Major sixth - 9 semitones.
• Minor seventh - 10 semitones.
• Major seventh - 11 semitones.

The notes of a scale are numbered by their steps from the root of the scale.

https://en.wikipedia.org/wiki/Scale_%28music%29

Often, especially in the context of the common practice period, most or all of the melody and harmony of a musical work is built using the notes of a single scale, which can be conveniently represented on a staff with a standard key signature.

https://en.wikipedia.org/wiki/Common_practice_period

Common-practice harmony is almost always derived from diatonic scales and tends to follow particular chord progressions that have withstood the test of time.