How do the modes relate to traditional Celtic music?
For the most part, traditional Celtic music uses four of these modes: Ionion, also referred to as major; Aeolian, also referred to as natural minor; Mixolydian and Dorian. When we hear tunes that sound minor, they are often times in the Mixolydian or Dorian modes. The flat 3 and 7 in Dorian gives it a minor sound. Even though the Mixolydian mode is closely related to the major scale, it’s characteristic of a flat 7 gives it a minor flavour.
It is interesting to note that the Highland bagpipe scale is essential the Mixolydian mode. The pipe chanter has a range of 9 fixed pitches: G A B C# D E F# G A. If we start on A, this gives us the Mixolydian scale. This is the reason why so many tunes in the Scottish and Cape Breton repertoire are composed in this key. There are versions of tunes in Cape Breton that were originally in natural minor but switched to Mixolydian. This is most likely because the Highland pipes were just as common, if not more common, than the fiddle in Cape Breton up until the middle of the last century and fiddlers were very much accustomed to hearing tunes played in this mode.
Why should I know about these modes?
For the most part, we are familiar with looking at key signatures of major and minor scales. However, in some tune books, instead of using a major or minor key signature with accidentals in the melody when the tune is modal, the key signature represents the mode. If you are not aware of what modes are, this can be confusing. For example, if a tune is in A Dorian, the key signature will have an F#. But this is also the key signature for G major and E minor.
If you are an accompanist, it is important to recognize the difference between the Dorian and Mixolydian modes. I’m going to use the tonal center of A as an example. Because a tune sounds minor, it can be easy to assume that the A chord is minor. However, A Mixolydian uses an A major chord because that scale contains a C#; the Dorian mode uses an A minor chord because that scale uses a C natural. It’s not necessary to know the names of these modes, but it’s important to be aware of the melody and what chords the melody is producing.
As a fiddler, it is empowering to be aware of these differences. Tunes like “King George the IV” which alternate between both A Mixolydian and A Dorian can be difficult for accompanists who aren’t familiar with the tune because, in the case of King George, it uses an A minor chord in the first half of the tune and an A major chord in the second half. The melody contains both C#’s and C naturals. Again, it is not necessary that you know the names of the modes, but it can be important inform your accompanist when the melody contains two different qualities of 3rds as in the case of King George- a C# and a C natural- so they will know when to use an A major chord or an A minor chord.
I hope you have found these posts useful. Please feel free to post any further comments or questions.