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Tonal degrees and degree tendencies

In the hierarchy of tonal degrees, the most important is the tonic or keynote. The prevailing model of tonal functions developed by Hugo Riemann in the 19th century places emphasis on the 1st, 4th, and 5th (the tonic, subdominant, and dominant) degrees.

It is, however, possible to perceive the hierarchy of tonal degrees differently; certain degrees hold a special status in comparison with the other degrees of a key.

According to the current model of tonal perception, the tonic is the most stable degree in the hierarchy. The other notes of a major triad are also included in the group of stable degrees. The other degrees of the key are less stable; all altered notes are unstable.

In the example below, minims imply the stable degrees of a major and a minor key. Unstable degrees are marked with crotchets. A melodic line often tends to move from an unstable degree towards the closest stable degree.  It is common for melodies to end in either hat  - hat or hat - hat. Degree numbers are often written with a circumflex to distinguish them from, for example, interval numbers.

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The letters T and S denote a tone (a whole step) and semitone (half step), respectively. A semitonal relationship between two degrees is perceived to be more solid than a corresponding tonal relationship. We often use the term "tendency tone" when discussing the progress of a melody. The best-known tendency tone is the leading note hat. The same idea is sometimes associated with hat, often leading to hat. Furthermore, all chromatic notes are tendency tones and therefore highly unstable.

In a major key, hat and hat are inclined to lead to hat and hat since there is a tritone between them. In a harmonic minor scale, there is a tritone also between hat and hat, which makes a transfer to a relative major scale natural as hat and hat in a harmonic minor scale are hat and hatin a relative major scale.

The figure below shows an alternative way of observing degree relationships in a major key. In the end, melodies move from other degrees and their chromatic alterations to the first degree, shown as the largest numbers in the diagram. Only slightly smaller are the 3rd and 5th degrees (a tonal melody can end in either of these two). The other degrees are unstable, and the arrows show typical directions of voice leading. The most unstable degrees (thick arrows) are the leading note and chromatic alterations of other degrees, often momentary and showing a strong tendency toward the root note.

A semitone apart from the next diatonic degree up, degrees 3 and 7 are not assigned a sharp sign. The 1st, 4th, and 5th degrees are not flattened in notation.

Relationships in a major key

In minor keys, degree relationships differ to some extent from those in major keys. A common scale, the harmonic minor is the basis of degree numbering. Thus, the 7th degree in the diagram below does not comply with the key signature (for example, G in A minor) but describes the leading note of a harmonic minor (G sharp).

Relationships in a minor key

The various types of minor scales are different from each other with respect to the degrees of the upper tetrachord. In a melodic minor, the degree progression is often 5–#6–7–1; going down it is often 1– flat7–6–5. There are, however, several exceptions to this rule. This is why flat7 can have a tendency to go in both directions.

The most typical tendencies (in a major key) can be shown in one diagram with the help of solfège syllables:

Most typical tendencies in a major key

The diagrams are intended to show degree relationships and to instruct us in writing chromatic signs. It is commonplace, for example, for notation software to produce accidentals in an inappropriate manner. Musicians, however, are used to reading music with a familiar musical logic.

In major and minor keys, both the key signature and the chromatic alterations are determined by the tonic. For example, a melody in C major always has an F sharp between F and G. Correspondingly, A major always has a D sharp (not E flat). Chromatic alterations can't be written in any other way except for chord progressions where chords with the same form proceed in parallel motion. This is common especially in African-American music: the F sharp mentioned before is G flat in the progression Aflat7 - G7.

Below is a list of names for scale degrees.


1. 1st degree

tonic, keynote

2. 2nd degree

supertonic

3. 3rd degree

mediant

4. 4th degree

subdominant

5. 5th degree

dominant

6. 6th degree

submediant

7. 7th degree

 

Other names for the leading note are leading tone (Am. English), sensibile (Italian)and Leitton (German). The term subtonic usually denotes the lowered 7th degree.