Scales, Modes, and Irish Music
Here follows a post to IRTRAD-L by my friend Philippe Varlet.
The most common SCALES are MAJOR and MINOR. One starts with a major 3rd (D to F# for instance), the other with a minor 3rd (D to F natural). These scales are made of whole- and half-steps, with in particular a 1/2 step between the 7th note (called "leading tone") and the tonic or "home note."
For instance, D major:
D E F# G A B C# (D) whole whole half whole whole whole half
In Irish instrumental music, the MINOR SCALE is very rare, the MAJOR SCALE is the most common. However, Irish tunes are also built on MODES of the MAJOR SCALE. The MODES are given Greek names in reference to old Greek and medieval music theory, but are also called mode 1, 2, 5, 6 (these are the ones found in Irish music) depending on which note of the MAJOR SCALE they start on.
For instance, using the D major scale:
1 2 3 4 5 6 7 Major (Ionian, mode 1) D E F# G A B C# Dorian (mode 2) E F# G A B C# D Mixolydian (mode 5) A B C# D E F# G Aeolian (mode 6) B C# D E F# G A
The DORIAN and AEOLIAN modes sound minor because they start with a minor 3rd, like the MINOR SCALE--however, they do not have a leading tone. The DORIAN mode is by far the more common of the two. If you hear an Irish tune that sounds minor, it is likely to be in DORIAN. To make sure, listen to the 6th note, it is a 1/2 step higher in DORIAN than it is in AEOLIAN. For instance, E DORIAN (see above) has C#, while E AEOLIAN would have all the same note except for C natural.
The MIXOLYDIAN mode sounds major, but also doesn't have a leading tone. Sometimes, it is described as having a flat 7th note, because it is a 1/2 step lower than a leading tone would be in the MAJOR SCALE.
Another important characteristic of how these modes are used are their harmonic implications. That is, the tunes are built around certain chords, and these sets of chords vary with each mode.
MAJOR (mode 1) tunes are usually built primarily around the I-IV-V chords, the three major chords of any given major key. In D Major for instance, the chords would be D Maj, G Maj, and A Maj.
Tunes in other modes are typically built around TWO CHORDS only, which are a step apart. DORIAN and AEOLIAN (modes 2 and 6) will have a minor "home" chord and a major "contrast" chord a step below. MIXOLYDIAN (mode 5) tunes will have two major chords. For instance, for modes of the D Major scale:
E Dorian E minor and D Major A Mixolydian A Major and G Major B Aeolian B minor and A Major
This is a very basic scheme, but it's a good start for an accompanist who has never heard a tune before and who can spot these chords and build from there.
You can apply this to other scales. The other most common MAJOR SCALE in Irish instrumental music is G MAJOR, with associated MODES: A Dorian, D Mixolydian, and E Aeolian. And so on.Philippe Varlet
(In addition to being a Font of Wisdom and a fine fiddler, Philippe is the proprietor of Celtic Grooves Imports, a great source for imported and small-label Irish music recordings.)