Modes
The term modal is generally used when describing music written before the major
and minor scales became pre-eminent,
that is, music from approximately 300 AD to 1600 AD.
The modes have a different arrangement of tones and semitones
to the major and minor scales, as outlined in the first table below.
For well over a millenium the modal system provided the foundation from
which plainsong (or chant)
and much folksong was created.
Plainsong is unaccompanied melody; its melodic and
rhythmical complexity contrasts with the seeming
simplicity of the limited choice of notes available in a mode.
The early composers of plainsong were typically monks who believed that music should bring
the faithful closer to God, and was therefore to be used for ceremonial and ritualistic purposes1.
The ecclesiastical modes (also called traditional or church modes) differ from the modern
major and minor scales not only in their disposition of tones and semitones, but also in the way that
certain melodic patterns or formulae tend to be associated with a particular mode2.
The patterns are subtle, but they are important.
The same principle is apparent in blues and jazz, in which there are many idiomatic figurations
(usually called riffs) that are used by experienced musicians to give the 'genuine' sound to the music.
The following tables show the basic structure of the modes. The range column refers to the 'white' notes on the piano which encompass one octave of the mode. For example, the range of the Dorian mode is specified as d to d' (from d to the octave above), therefore the notes of the Dorian would be as in figure 1. Of course the mode can be transposed to any pitch, so the Dorian mode can be based at C as in figure 2.
| figure 1 | figure 2 |
|---|
 |  |
The T/S grouping column shows the disposition of tones and semitones in the same way as was explained for the major scale on the Scales page.
| mode | range | T/S grouping |
|---|
| Dorian | d - d' | T S T T T S T |
| Phyrgian | e - e' | S T T T S T T |
| Lydian | f - f' | T T T S T T S |
| Mixolydian | g - g' | T T S T T S T |
| Aeolian | a - a' | T S T T S T T |
| Ionian | c - c' | T T S T T T S |
The first four modes in the table above are known as 'authentic' modes.
The Aeolian and Ionian modes were later additions to the theory of the modes.
The Aeolian is identical to the 'natural' minor (the descending melodic minor) and the Ionian is the same as the major scale.
The following table shows the system of eight modes (four pairs) as given in the oldest theoretical
references (circa the 9th century AD).
This includes the 'plagal' forms
of the modes, which have the prefix Hypo. The plagal version of a mode starts a 4th
below the 'authentic' version.
The 'final' is the note on which the plainsong
typically ends.
The 'dominant', also known as the 'tenor' (see the online
Encycopedia Brittanica), is a note which is next in importance to the 'final'.
| mode | Latin name | final | range | dominant |
|---|
| Dorian | Protus authenticus | d | d - d' | a |
| Hypodorian | Protus plagalis | d | A - a | f |
| Phrygian | Deuterus authenticus | e | e - e' | c' |
| Hypophrygian | Deuterus plagalis | e | B - b | a |
| Lydian | Tritus authenticus | f | f - f' | c' |
| Hypolydian | Tritus plagalis | f | c - c' | a |
| Mixolydian | Tertrardus authenticus | g | g - g' | d' |
| Hypomixolydian | Tertrardus plagalis | g | d - d' | c' |
1. For example, around 750 AD St. John Damascene of Damascus was
composing groups of hymns which were used in an eight-week cycle for church services.
Each group was written in one of the modes; a group would be sung for a week,
the following week a group in the next mode would be used, and so on, so that
after eight weeks the modal cycle would begin again with a fresh set of hymns.
2. In medieval Russian chant the first mode has approximately 90
of these patterns.