Diatonic scale

Modern piano keyboard based on the diatonic scale. The Do note is more on the left of the image and seven white keys on the right, a sharper octave.

The diatonic scale is a musical scale made up of intervals of consecutive seconds.

The word "diatonic" comes from the Greek word diatonikós (διατονικός), which essentially means "through tones", which in turn comes from diatones (διάτονος), "separated to the maximum", referring to the maximum possible distance between the semitone intervals in them, compared to other scales, in which they appear closer.

In the common practice of classical music, the types of diatonic scales are simplified by reducing them to two variants or modes: the major (major diatonic scale) and the minor (minor diatonic scale). Minor second intervals separated by a semitone (mi-fa and si-do) and major second intervals separated by whole tones (do-re, re-mi, fa-sol, sol-la, la-si). This scale has seven intervals per octave, the eighth note being the repetition of the first but more acute or serious.

On a keyboard instrument the white keys correspond to the diatonic scale of do, as shown below and where C-D-E-F-G-A-B is the alternative notation to Do-Re-Mi- Fa-G-La-Si.

Graphical outline of a 3 octave keyboard, which indicates the positions of the notes using the Anglo-Saxon musical notation system.

Major Diatonic Scale Formula

To form a diatonic scale in a major mode, you take a progressive series of 5 diatonic chords that are used as perfect fifths and a diminished and augmented fifth, starting with the tonic. In the key of C major, for example, this is indicated as follows:

The ordering of all the scales by joint degrees of the notes of this series of fifths produces the diatonic scale of C major as indicated in the following graphic:)

The resulting major scales of the first type consist, in order, of the following tones (T) and semitones (st): T-T-st-T-T-T-st (two tones, semitone, three tones, semitone). Applying the above formula for the C Major Scale, would result in the sequence:

It should not be forgotten that the scale is completed with the octave, repeating the C of the next higher octave.

Relative minor

With the same notes of the major diatonic scale, another scale can be obtained, which is known as the relative minor of the original scale. Although it is possible informally to call this scale "the relative minor", it is actually the scale of the relative minor tone. Thus, the tones have a relationship between them known as major/minor relativity and indirectly their respective associated scales enjoy this same relativity. The diatonic minor scale is also called the Aeolian minor scale or the natural minor scale.

One way to find out the relative minor scale of each note is to descend in an interval of a minor third. This would be like this: if you are in the scale of C major and you go down a tone and a half, it would give us the note la (do-si-la descending). Therefore, the relative minor scale of C major is A minor, and it maintains the same key signature (ie: the same accidentals) although starting with the ' new' tonic (la in this case).

Example

The A minor scale, following the terminology explained above, is the scale of the relative key minor of C major. Conversely, the C major scale is the scale of the major relative pitch of A minor.

The relativity between tones, and indirectly, between scales, tells us that they are made up of the same group of notes but they are located in a different position with respect to the root note. For example, the most characteristic part of the scale in a major or minor mode are the first four notes or first tetrachord; if in the major it is Tone-Tone-semitone, in the minor it is Tone-semitone-Tone. This places the third note one semitone lower in the minor mode than the major, and the tonic triad chord the characteristic sonority commonly known as a "minor chord" or "major chord", respectively.

When comparing the major and minor (natural) diatonic scales, two more differences can be seen, apart from the already exposed difference of a semitone lower for the third. In the minor scale the sixth and seventh notes are also one semitone below their respective notes in the major scale. Thus, the intervals that the third, sixth and seventh notes form with the tonic are one semitone less than the corresponding major ones, and thus these intervals are called minor third, sixth and seventh, unlike those of the major mode. which are called seniors.

The rest of the notes: fundamental, second, fourth and fifth do not vary between the scales of the major and minor modes when considering two scales with the same root, nor their intervals from the root or tonic note, whatever let it be this

Types

Using only single accidentals, 30 diatonic scales can be produced, 15 in the minor mode and 15 in the major mode. Theoretically it is possible to use diatonic scales with double accidentals and in this case 28 more scales can be produced.

Each of the two diatonic scale modes has four different scale types. The four types of scale of the major mode are formed by means of the series of natural sounds of the physical-harmonic law, plus the three combinations that can be made by taking the sixth and seventh degrees of the minor mode.

Taking the keys of C major and C minor as an example, the following four types of scale can be produced from the major mode and the minor mode:

Higher mode: do greater.	Lower mode: do minor.
First guy. Natural scale.	First guy. Natural scale.
Second type: Sixth grade of minor mode.	Second type: harmonic. Seventh grade of the major mode (as natural B is the distance it has with the tonic is of a semitone not of a tone),
Third type: melodic. Sixth and seventh grades of the minor.	Third type: melodic. Sixth and seventh grades of the elder and when descending it becomes a smaller natural scale.
Fourth guy. Seventh grade of the minor mode.	Fourth type: rhetoric. High grade.

As can be seen, of the three modal degrees (3rd, 6th and 7th) the third is invariable and cannot change on the scale so that it retains its modal characteristic. The other two degrees, the sixth and the seventh, can belong to the two modes, although this does not mean that they transform into degrees differently, but rather that they lend the various types of diatonic accidentals to the scale with their own modality.