Suomeksi | In English

Key and scale

Key and scale are two of the most essential concepts in tonal music, so it is important to know them more thoroughly than just as musical terms.

Prior to the 17th century, music theory was based on hexachords (see Hexachords). They were prominent in music theory for a long period, also by the time of writing music in major or minor keys and not, for example, in the Dorian mode. The 12 major and 12 minor keys as we know them were not established until the 18th century.

Major keys and major scales share one characteristic: a tonal centre. A decisive difference is that a composition may consist of a greater number of notes with different pitches or note names than the relevant diatonic scale.

The notes outside of a scale are called altered notes. They are notes altered chromatically (chroma = colour) from the notes of a major or a minor scale. For example, the note B originally had two different colourings, the current B flat and B (see Chromatic symbols). A change in the "colour" or timbre of a note creates a certain tension inside a key. All chromatically altered notes are known as active notes (see Tonal degrees and their tendencies).

Bar one in the example shows a C major scale as it is usually presented. Bar two shows a harmonic C minor scale. It is different from the key signature for C minor (three flats) because in minor keys the seventh degree (leading note) is usually raised. In bars three and four, the same notes are written as simple melodies, and one can clearly perceive the differences in the third and sixth degrees of a major and a minor note. Bar five shows the diatonic notes of D minor written as degrees. Possible altered notes of D minor are seen in bar six.

Scales on staff

In a major key, the usual chromatic alterations include #4 and flat7 (in C major, F sharp and B flat), which refer to the keys in G and F major. It is usually not considered wise to write the C major scale as C, D, E, F, F sharp, G, A, B flat, B; notation is based on seven-tone (heptatonic) scales, and music theory is strongly bound to the notation tradition of our time.

Melodies in minor keys (for example, Finnish tangos) may include several chromatic alterations: the melody of Sateen tango ("tango of rain") by Unto Mononen has several auxiliary notes and, through them, the altered degrees of  flat2, #3, #4, #6, and flat7, which are not accordant with a harmonic minor scale. The example consists of fragments of the melody:

Chromatic alterations

The total number of notes or pitches with different names is 12 (7+5), which includes all the possible pitches of, for example, the piano. It should be noted, however, that because flat2 and #1 derive from two different diatonic notes, they are considered different notes.

The term chroma denotes a "group" of 12 pitches. In tonal music, it is fairly rare that all the 12 pitches are used in one composition, as an excess of altered notes in any other than non-harmonic positions may weaken the links with traditional tonality.

A composition can be perceived clearly as major or minor, even if the scale used is (major or minor) pentatonic. The timbre typical of a major or minor scale can be achieved by applying as few as three different pitches if they are from the beginning of a scale.

The term tonal (or tonality) is used when a melody is perceivably linked with a key.

The term modal is used in several senses: on one hand, it denotes the opposite of tonal, in other words a modal melody is based on diatonic modes or other scale forms (for example, 1950s modal jazz).

On the other hand, the phrase "modal alteration" implies that an individual chord is in a parallel key, for example that there is an F minor chord instead of an F major chord in C major. What is essential is that the keys/scales share the same tonic value.