This tune is in the key of G ionian. This means the available chords are G major, A minor, B minor, C major, D major, E minor and F# diminished, with the main ones being I, IV and V aka G, C and D.
There is a key change in the B part, to A dorian. The chords in this mode are the same ones available in G ionian, but because we are now beginning and ending our key scale on A, the main chords are I, IV and V beginning from A, aka A minor, D major and E minor.
There are no strongly chord IV sound sections in the A part of the tune, so I have stuck to chord I (G) throughout. Chord V, as always, goes in bar four and in bar eight chord V returns to chord I to mark the end of the section. This is the “seventh foot tap rule”- you tap your foot twice in each bar and on every seventh foot tap there is always a chord V.
In the B part we have switched keys to A dorian. You can tell because the first bar contains the notes “E A A G A – G A”. You generally work out which chord family fits with a section of melody by which notes are played on the dominant beats (the ones where your foot taps). In this section the dominant notes are E, A, A, G (followed swiftly by A). As A, C and E are the notes of an A minor chord this clearly shows that a shift to A minor has taken place. The most common of the two minor modes in folk music is the dorian (optimistic minor) and A dorian contains the same notes as G ionian, so it is safe to assume that the B part is in a dorian not A aeolian. This is later confirmed by the inclusion of the F# note which would be F♮ if the part were in A aeolian.
The third bar of the B part starts and finishes on G, so I have put a G chord with it. Resolving from G – Am (chord VII – chord I) instead of Em – Am (chord V – chord I) in the fourth bar works because G major is related to E minor. Every minor chord has a related major chord, which is two above it in the key scale, and these two can always be used interchangeably. In this case E is the 5th note in the scale of A dorian. Two notes above E in the scale is G, so G major can replace E minor for a lighter feeling chord progression.
In the last two bars of the B part you will noticed that I have not ended on A minor as you would expect for a section in the key of A dorian, but on D. This is because I know the tune is about to switch back to G ionian for the A part, so I end the section on G’s V chord, which then wants to resolve back to G to start the next section. Any time a key change is coming up you can always end the current section on the upcoming key’s chord V in order to make the modulation (key change) work.
In this version I have replaced G in the second bar with its related minor, E minor. In order to link these two chords together, I have played an intermediate chord D/F#. This works well because the bass note in the second chord creates a nice bassline – G, F#, Em. It is always nice to link a major chord to its related minor in this way- you can find a complete list of these types of linking chords in my first book, Backing Guitar Techniques For Traditional Celtic Music.
Replacing the G from the third bar with a C works because you can always replace a chord I section with chord IV, or a chord related to chord IV. Therefore, either C or its related minor Am are valid substitutes for a chord I section. In this instance I have linked C to Am using another linking chord, G in the first inversion, otherwise known as G/B. You can find a diagram for this chord below.
I have also used the G/B chord to create bass movement in bar seven. This chord sounds fine in context because it’s an inversion of chord I, and this is a chord I section.
In the B part I have used two minor substitutes for G major in bars three and four. G major’s related minor is E minor, and a major chord can also be substituted to the minor chord whose root is two above its own in the key scale. In this case that is B minor (G – A – B).
The last two bars of the B part use a chord progression which would commonly appear in G ionian, to make it clear that the tune still has its roots in that mode; C – D. This would be chord IV – V in G ionian, and would traditionally be followed by G major (chord I). In the first playthrough of the B part the last chord is A minor as the tune is going to continue in that key, but on the second playthrough it reverts to G major ready for the A part which is back in the original key of G ionian.
In this version I have added nice jazzy tetrads (four note chords instead of the usual triads or three note chords). When adding tetrads or more complicated “jazz” chords into folk music in major keys, chords I and IV become major 7 type chords, chords II and VI become minor 7 type chords and chord V becomes a dominant type chord. You can learn a lot more about how to implement these types of chords in my book Backing Guitar Techniques for Traditional Celtic Music. For our purposes the complete list of available tetrads is: G major 7, A minor 7, B minor 7, C major 7, D (dominant) 7, E minor 7 and F# ½ diminished (again, if you want to understand what a “half diminished chord” is then please see my book).
For the A minor 7 chord in the B part, I like to use the barre chord version (pictured below). I then like to use the high E minor and B minor barre chords which are nearer to this chord than the more common voicings found lower down the neck. Generally speaking, B parts are usually higher pitched and more energetic than A parts, so I often match this by using higher chords (incorporating low open strings as bass notes where possible) in my backing.
In bar four of the A part I have used D9 instead of D7. You can theoretically add ANY notes to a jazzy chord V in a major key, so any dominant or altered dominant chord would do. However the ones I particularly like the sounds of are 9 and 13 chords. Experiment with using these chord types in place of V chords in other keys!
In bar seven of the A part I have used the chromatic link Cmaj7 – C# ½ diminished – D9. This works well because any time you have two chords whose root notes are separated by a tone, you can always link the two by using the diminished or ½ diminished chord whose root lies on the semitone in between them. This works well if you are ascending- if you wish to create a descending chromatic link then using a dominant 7 chord works better, eg D9 – C#7 – C major 7.
In the B part I have used the same tricks mentioned above to convert my substitutions version of the tune into a jazzier version of the same progression. Note the chromatic link reappears in bar seven.