MusicA Beginner's Guide to Modal Harmony


Medieval musicThe kind of harmony taught in most university music courses deals with what is known as the "common practice" era, i.e., the kind of things that most composers did in the period approximately 1650-1850. After 1850, composers started to experiment more with harmony. But traditional Irish and Scottish music has been more conservative than classical music; it tends to stick with the kind of harmony used before 1650, which is modal harmony. The use of the modal system provides great advantages in the analysis of traditional music. Lest you think I'm making all this up, here's a quotation from the well-known London-based fiddler Peter Cooper:


    Anyone familiar with written violin music but not with folk music may be perplexed by some of the key signatures used. This is because Irish tunes are not constructed within the diatonic (major and minor) idiom of classical music but in the older system of modes. It is not necessary to understand the theory of modes to play the tunes and you may prefer to skip this section. But four modes are used in Irish music, two that sound 'major', two that sound 'minor'. They are called the Ionian, Mixolydian, Dorian and Aeolian modes and correspond to the scales you'd get if you played only the white notes of a piano, starting on C, G, D and A respectively.

    The Ionian mode sounds exactly the same as the major scale and is the most common - over half the tunes here are in the Ionian mode. The Mixolydian mode resembles the Ionian but includes a minor seventh. Tom Billy's Jig, for example, is in the Mixolydian mode of A and has a G natural instead of G#. Its key signature - two sharps - does not indicate the key of D major. The Dorian and Aeolian modes are alike in having a minor third, but are distinguished by having a major and minor sixth respectively. Cooley's Reel, for example, is in the Dorian mode of E and has two sharps, F# and C3. The Rights of Man is in the Aeolian mode of E and, with a C natural instead of a C# as its sixth, has a single sharp as its key signature.

        Peter Cooper
        Mel Bay's Complete Irish Fiddle Player
        Mel Bay Publications, 1995
        pp. 19-20


Since the historical background is interesting, I'll give a short sketch of how modes came into use. Then I'll give a brief introduction to the modal harmonic system as used during the Renaissance, which is still in use today in traditional Scottish and Irish music.


The modal system derives from ecclesiastical chant. In the late 4th century, Ambrose, Bishop of Milan, defined four modes, to which he gave numbers. The nature of each mode is defined by the position of the semitones in the scale:


Ambrosian Modes

1st tone d e f g a b c d
2nd tone e f g a b c d e
3rd tone f g a b c d e f
4th tone g a b c d e f g


This system was modified under the direction of Pope Gregory (Pope in the period 590-604) by increasing the number of modes to eight. The four additional modes were produced by starting each of the Ambrosian modes a fourth lower, so that the keynote appeared in the middle of the scale. The four ancient modes were called authentic; the new modes were called plagal:


Gregorian Modes

1st tone Authentic De f g a b c d
2nd tone Plagal a b c D e f g a
3rd tone Authentic E f g a b c d e
4th tone Plagal b c d E f g a b
5th tone Authentic F g a b c d e f
6th tone Plagal c d e F g a b c
7th tone Authentic G a b c d e f g
8th tone Plagal d e f G a b c d


Chant MSThis was the system specified for the Gregorian chant. Around 1020, the monk Guido of Arezzo gave names to the notes based on the first syllables of each line in the Hymn for St. John the Baptist's day (composed by Paul the Deacon c. 774):

      UT queant laxis
      REsonare fibris
      MIra gestorum
      FAmuli tuorum:
      SOLve polluti,
      LAbii reatum, Sancte Johannes

SI as the name for the 7th degree of the scale was not agreed upon until the late 1600s. The use of DO in place of UT was proposed in 1673 by Giovanni Maria Bonocini; it has not been universally adopted to this day.


Lute trioAs can be seen from the table above, Gregorian chant used only what we would now think of as the white notes of the piano. Chant consists of only a single melodic line. But as polyphony developed through the Middle Ages, the tritone interval between B and F became a problem. This was solved by the introduction of B flat, which originally was not thought to be a different note, as we do today, but as a modification of the original note B. As time passed, additional modifications were allowed (although the strict church system still allowed only B flat). This gave rise to modes that could not be described using the original Gregorian system.


The system we use today is based on the compositional practice of the Renaissance period. In the 16th century Glareanus assigned Greek names to each of the existing modes. (These names are not connected to any system actually in use in ancient Greece.) The distinction of plagal and authentic has been abandoned. The Renaissance system was as follows:


Renaissance Modes

Mode Name Notes Scale pattern
Ionian c d e f g a b 1 2 3 4 5 6 7
Dorian d e f g a b c 1 2 -3 4 5 6 -7
Phrygian e f g a b c d 1 -2 -3 4 5 -6 7
Lydian f g a b c d e 1 2 3 +4 5 6 7
Mixolydian g a b c d e f 1 2 3 4 5 6 -7
Aeolian a b c d e f g 1 2 -3 4 5 -6 -7
Locrian b c d e f g a 1 -2 -3 4 -5 -6 -7


Thus, with a key signature of no flats or sharps, seven possible modes, or scale patterns, can be represented. (In fact, because the fifth degree of the scale is not perfect, the Locrian mode is of theoretical interest only—it has rarely been used in practice.) Of course, any starting note can be chosen—every key signature can generate seven possible modes. In the Renaissance, however, not all notes would have been allowed as starting notes.

Next the same table is given with the starting note being C in each case. Now each mode starting on C will have a different key signature.


Renaissance Modes, C starting pitch

Mode Name Notes Scale pattern Key signature
Ionian C D E F G A B 1 2 3 4 5 6 7 No flats or sharps
Dorian C D Eb F G A Bb 1 2 -3 4 5 6 -7 Bb Eb
Phrygian C Db Eb F G Ab Bb 1 -2 -3 4 5 -6 7 Bb Eb Ab Db
Lydian C D E F# G A B 1 2 3 +4 5 6 7 F#
Mixolydian C D E F G A Bb 1 2 3 4 5 6 -7 Bb
Aeolian C D Eb F G Ab Bb 1 2 -3 4 5 -6 -7 Bb Eb Ab
Locrian C Db Eb F Gb Ab Bb 1 -2 -3 4 -5 -6 -7 Bb Eb Ab Db Gb


In traditional music, the most commonly used modes are the Ionian, Dorian, and Mixolydian. The Aeolian mode is not uncommon; the Lydian and Phrygian modes are extremely rare. The Locrian is never used.

In the Baroque period of music, all modes except the Ionian and Aeolian were discarded. These were then renamed the major and minor scale. However, in actual use, the minor scale is often modified by the use of a raised 7th degree leading tone. This usage derives from the medieval and Renaissance use of musica ficta—these were adjustments made to certain notes (what we now know as accidentals) to avoid forbidden harmonic relations such as the tritone, or for other reasons dealing with vertical harmonic relationships.

Irish dance Since traditional music consists of a single melodic line only, without harmony, musica ficta was never used. Hence raised leading tones in the Dorian and Aeolian modes are never encountered.


A large portion of the stock of traditional tunes seems to have originated in the 18th century. These tunes almost always stay in a single mode. Tunes composed in the 19th century, however, sometimes change modes. For example, Chief O'Neill's Favourite Hornpipe is in D Ionian, except for measures 3-4 of the A section, which are in D Mixolydian, and the first four bars of the B section, which change to a D Dorian. This is a slightly unusual case, but similar modal changes are encountered in other tunes from the nineteenth century.

It was not until the early 20th century that researchers in traditional music realized that traditional music used Renaissance modes. The pioneering work of the likes of Cecil Sharp and Ralph Vaughan Williams was greeted with statements along the lines of "How can you tell me that these ignorant peasants are singing in the Mixolydian mode when some of our finest music professors don't even know what it is?" However, the fact is now generally accepted by ethnomusicologists. The interesting research area has moved on to the examination of how, in certain circumstances, some degrees of a mode can be modified by intervals less than a semitone. (This is a feature mostly found in the playing of older musicians—the influence of mainstream equally-tempered music is driving this artistic device into oblivion.)

    Some Irish tunes are constructed on gapped scales. They have only six rather than the usual seven different notes within an octave. The third is missing, for instance, from The Walls of Liscarroll while Brian Boru's March lacks the sixth and both have a rather archaic sound. Another very ancient feature of the scales used in some Irish music is the inclusion of 'half-sharp' notes—quarter tones mid-way between natural and sharp.

        Peter Cooper
        Mel Bay's Complete Irish Fiddle Player
        Mel Bay Publications, 1995
        p. 20


Nineteenth-century editions of traditional music frequently "corrected" tunes by adding sharpened leading tones, changing Dorian mode to Aeolian mode, etc. Hence, such sources should be regarded as suspect. Eighteenth-century collections appear to be fairly reliable; if the tune has lasted into modern times, it usually is fairly close to the eighteenth-century setting. Otherwise, a setting collected in the twentieth century is preferable.

The use of the modal system is particularly convenient in the matter of key signatures. For example, when writing an A minor tune in a key signature of no sharps or flats, if it is noticed that every occurence of an F has been sharped, it should be concluded that the tune is in the mode of A Dorian rather than A Aeolian. This can be reflected by placing an F# in the key signature; the avoidance of unnecessary accidentals is a convenience both to the transcriber and to the performer.

Some editors place natural signs in the key signature of Dorian and Mixolydian mode tunes, e.g., a B natural for the D Dorian mode or a G natural for A Mixolydian. The sole function of this is to reassure performers who are unfamiliar with modal notation that this is indeed what is intended.


It should be noted, however, that in Scottish music, the "Northeast" style in particular has been influenced by a number of classically trained performers, the most renowned of which are William Marshall and J. Scott Skinner. This particular style features a greater use of the major/minor tonal system, although Mixolydian tunes are still quite common. Other features are the use of classical bowing techniques such as staccato and spiccato, and classical-type changes in dynamics.

Modern performers in this style usually use a constant Kreisler-style vibrato. This is undoubtedly a modern innovation—it is hardly likely that traditional fiddlers were using a constant vibrato before the classical violinists started to! In fact, this can be confirmed by recordings. Marshall lived before the invention of recording, but J. Scott Skinner (1843-1927) recorded extensively between 1899 and 1922. His playing is very interesting, mixing classical bowing styles, portamento and position playing with a traditionally ornamented style reminiscent of Cape Breton fiddling. He uses almost no vibrato at all, just like classical violinists of the late 19th century. The "Northeast" style has been promulgated mostly through written music, rather than by ear like most traditional music. Thus today's performers in this style follow conventional 20th century stylistic norms, rather than attempting to recreate the composer's intentions, as documented on his recordings. But to be fair, why should Skinner receive any better treatment than is given to Brahms or Schubert, whose works are similarly modified by modern performers?

The use of major/minor tonality in this one particular context is likely to be correct as far as the intentions of the composer are concerned. However, if such tunes achieve any popularity among traditional fiddlers, as some of Marshall's and Skinner's have done, they are usually modified into a modal tonality.

Other regional Scottish styles have never adopted any of these classical performance devices, or the major/minor harmonic system; the same is true of all regional Irish traditions—excepting only the one-man "tradition" of Seán Maguire!



Jack Campin's tutorial on the modes of Scottish traditional music. Here's a bit of the intro:

    The descriptions of scales in music textbooks oriented towards Western art music usually give a misleading idea of the way they are used in Scottish traditional tunes. This document is intended to help Scottish traditional musicians undo some of the damage done by high-school music teachers while not taking off into irrelevant side-issues. All the theory here is illustrated by some real Scottish music.


Patricia Vivien Yarrow's A Brief Introduction to Modes in Early and Traditional European Music includes the old church modes and various other scale types.



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