The Four Modes of Irish and Oldtime music – in a nutshell

The four most common modes in Irish and Oldtime music are Major, Minor, Mixolydian and Dorian.

Major (AKA “Ionian”)

Like the regular major scale

Steps = Whole, Whole, Half, Whole, Whole, Whole, Half
Example:  C to C on white piano keys

Minor (AKA “Aeolian”)

The natural minor scale; like the Major with a flattened third, sixth and seventh

Steps = Whole, Half, Whole, Whole, Half, Whole, Whole

Example:  A to A on white piano keys

Mixolydian (think of it as a major modal)

Like the Major with a flattened seventh note

Steps = Whole, Whole, Half, Whole, Whole, Half, Whole

Example: G to G on white piano keys

June Apple and Red Haired Boy are mixolydian tunes

Dorian (think of it as a minor modal)

Like the Minor with a raised sixth note

Steps = Whole, Half, Whole, Whole, Whole, Half, Whole

Example:  D to D on white piano keys

Ballydesmond Polka and Road to Lisdoonvarna are dorian tunes

 

Special Tip:  Most oldtime jams stick to the keys of D-major, G-major, A-major and (occasionally) C-major.  If you know the notes in these 4 major scales, you also have the common minor, mixolydian and dorian modes covered.  Here’s why: The tonal center changes but the notes stay the same.

D-major, B-minor, A-mixolydian and E-dorian all use the same notes:   
D-E-F#-G-A-B-C#-D-E-F#-G-A-B...

G-major, E-minor, D-mixolydian and A-dorian all use the same notes:   
G-A-B-C-D-E-F#-G-A-B-C-D-E...

A-major, F#-minor, E-mixolydian and B-dorian all use the same notes:  
 A-B-C#-D-E-F#-G#-A-B-C#-D-E-F#...

C-major, A-minor, G-mixolydian and D-dorian all use the same notes:   
C-D-E-F-G-A-B-C-D-E-F-G-A...

Forming chords in these modes

To form a standard 3-note chord in any of these modes, start on any note then select every other note after that until you’ve reached the 1-3-5 notes of the chord (it's hard for me to write this in a way that's clear).  But, for example, in the D-major mode (and B-minor, A-mixolydian and E-dorian modes) the notes used are D-E-F#-G-A-B-C#-D-E-F#-G-A-B, and so on.  To form a D chord in these modes, you use the notes D, F# and A.  (Do you see how we skipped the notes E and G to form this D chord?).  However, in the C-major mode, which also happens to use the same notes as the A-minor, G-mixolydian and D-dorian modes (C-D-E-F-G-A-B-C-D-E-F-G-A, and so on) to make a “D” chord you use the notes D, F and A.  We still skip the E and G notes, but notice how in this case the 3^rd of the “D” chord is an F and not an F#.  By flattening the 3^rd one half step like that it actually makes it a D-minor chord.  So in the modes of C-major, A-minor, G-mixolydian or D-dorian if the melody suggests a chord with D as the root, then you can assume that a D-minor chord would sound better than a D-major.  You can apply this formula to all chords.

This may be hard to grasp at first and even harder to implement on your instrument.  Although once you start to get a handle on the concept I think you’ll discover that Irish and Oldtime music is not as mysterious as it seems, and there isn’t as much to memorize as you might think.

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