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Structure of a Scale

The standard tuning system with which most people are familiar (the one that is used on any piano) is known as equal temperament. According to this system of tuning, the distance between octaves is equally divided into twelve consecutive notes. The technical definition of a scale is simply a series of notes selected from these twelve, so theoretically there is an infinite number of possible scales.

Each one of the notes from a scale is known as a degree; each degree of a scale has its own name but is often refered to by a Roman Numeral. For example, the standard major scale consists of the degrees: I, II, III, IV, V, VI, and VII. These labels are merely used to define the relationship between the notes of a scale; as such, the eighth note of a major scale is refered to as degree I since the eighth note is the same as the first, apart from the fact that it is an octave higher.

Any two scales can be distinguished by two things:

  1. The number of notes that they have in them (i.e. the number of degrees they have)
  2. The distance between their degrees

For example, you can build seven different scales using just the seven natural notes (the white keys on a keyboard), all you need to do is change the note that you start on for each scale. Since there are seven different natural notes, there are seven different possible starting points, hence seven different possible scales. The major scale has semitones separating degrees III-IV and VII-I (remember that the eighth note of a major scale is refered to as I).

Relative Scales

Relative scales are two different scales that share the same notes. For example, the major scale of C and the minor scale of A contain the same notes. They are both relative scales: C is the relative major of A, and A is the relative minor of C. The relative minor of a major scale is the same as the degree VI of the major scale, and the relative major of a minor scale is the same as the degree III of the minor scale.

More about the Minor Scale

You may not like to hear this, but there are (in fact) three different types of minor scale. All three have different degrees VI and VII:

  1. Natural minor: this is the one we’ve already looked at, and it consists of the same notes as its relative major. Hence the name natural.
  2. Harmonic minor: degree VII is raised to form an augmented second between Degrees VI and VII. It also puts a distance of a semi-tone between degrees VII-I. This forms a dominant chord or dominant 7th chord on the fifth degree of the scale (these new terms are explained below).
  3. Melodic minor: degree VI is raised along with degree VII to avoid the augmented second formed in the harmonic minor.

Other Names for Scale Degrees

These are the names of the degrees mentioned earlier:

Degrees and their Names

Degree Name
I Tonic
II Supertonic
III Mediant
IV Subdominant
V Dominant
VI Submediant
VII Leading Tone or Subtonic

Musical Modes

Musical modes refer to scales when applied to specific diatonic scales; the most widely known are the Gregorian modes, which are themselves part of a very old style of musical theory that eventually evolved into the major and minor scales during the Renaissance.

You don’t really need to know that much about musical modes in order to play the harmonica. However, after being largely forgotten for many years they made a comeback in Classical music and Jazz music; as such, variants of Gregorian modes are still used in modern Jazz. The use of these modes has lent itself to harmonica theory, and many of the Gregorian modes often appear in name; these include: the Dorian mode, the Phrygian mode, the Lydian mode, the Mixolydian mode. Other modes that appear in harmonica theory include: the Aeolian mode, the Locrian mode, and the Ionian mode.

Like all types of scale, each of the musical modes has their own type of character; for example, the Phrygian mode (also called the Third Gregorian mode) is still used strongly in Andalusian music (Spain) and has semitones separating degrees I-II and V-VI.

All these terms will be expanded upon when we cover harmonica positions in a later section.