This tune is in the key of E aeolian. This means that the chords available are E minor, F# diminished, G major, A minor, B minor, C major and D major. Because aeolian is the sixth mode, these are the same chords which would be available in G ionian (major). The main chords will be I, IV and V relative to E minor, aka E minor, A minor and B minor.
As the tune is in 9/8, each bear contains three blocks of three notes. You can pick one chord for each of the three blocks if you wish. When finding the chord I, chord IV and chord IV sections, bear in mind that a section may only last a third of a bar. The tune also has three parts rather than the more usual two. Some people would call this a “48 bar slip jig” (16 in the A part, 16 in the B part and 16 in the C part).
In the A part of the tune, the last block of three quavers in bar one contains one long F# note. For that reason this section could be seen as a chord V section, because of chord I, IV and V, only chord V contains an F#. For ease of playability I have used chord V’s related major. 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 B is the fifth note in the scale of E aeolian, and two notes above it is D, so D major can always replace B minor.
The last three quaver block of bar two contains the notes “F# E D”. The notes of a D major chord are D, F# and A so this section is firmly a chord VII/ chord V (recall that these two are interchangeable) section.
In bar 4 I could have continued to play E minor, but I have replaced chord I with chord IV, A minor. This works because you can play chord IV in place of any chord I section.
In the B part there are no sections which sound particularly like they need a chord IV or V. In slip jigs, because each bar contains three block of three quavers, and hence three foot taps, the usual rule about playing chord V on every seventh foot tap (whch applies in all other time signatures) becomes “Play chord V at least on every sixth foot tap, potentially for the whole fourth bar”. It’s not as snappy a rule, but it does the job! In this case, bar two contains the notes “A B B B A B D B A”. Only the third of these three blocks sounds like a chord V section to me, so I have played chord VII, chord V’d related major (Bm, chord V, would also have been fine, but it’s harder to play at speed).
In bar four however we find the notes “B – D G – E D B A”. This is much more clearly a chord V section as chord V, Bm, contains the notes B, D and F# and most of the notes in this section are either B or D.
In the C part we find a different melody but with a similar harmonic structure to part A.
In this version’s A part I have used D and Bm interchangeably. You can always swap chord V to its related major in any mode other than ionian.
In bar four I have replaced an E minor (chord I) with C (chord VI). This works because as well as its related major, whose root is two above its own in the root scale, a minor chord can also be replaced with the major chord whose root is two BELOW it in the root scale. This works because a C chord contains C, E and G and an E minor chord contains E, G and B- the two common notes make these two chords a valid substitution pair.
In a slightly more unconventional move I have begun the B part on C instead of E minor. I usually say you should start sections on their key chord (unless the melody clearly dictates otherwise) so that the listener has a firm idea of what key they are in. However, when playing in minor keys it is often nice to build tension by beginning a part on the chord whose root note is two below chord I’s in the key scale. In this case I deliberately avoid playing chord I anywhere in the section, always substituting it to C. This creates tension which then adds energy when chord I kicks back in in part C.
In the C part I have again replaced Em with G. I have also ended the section on chord IV. This can be a nice way to end an Irish tune- finish on chord IV instead of chord I! If you are in any mode other than ionian this will add a kind of lift to the end (try it in dorian and mixolydian too). If you are in ionian on the other hand it will leave the listener with a kind of wistful “grass might be greener on the other side” flavour.
In this version I have replaced each of the available chords in the key with the “right kind of tetrad”. In the simpler versions I used the more common three note chords called triads. These contain just a root, 3rd and 5th. A tetrad is a four note “jazz” chord which contains a 7th as well.
E aeolian is related to G ionian. Therefore the tetrads available are the same in both modes, aka:
G major 7
A minor 7
B minor 7
C major 7
E minor 7
F# ½ diminished (rarely used in folk music- we’ll replace it with chord V in the first inversion, aka D/F#)
So for our tune in E aeolian, the options are E minor 7, D/F#, G major 7, A minor 7, B minor 7, C major 7 and D (dominant) 7. These simply replace the equivalent triad from the old progression, so D becomes D7, G becomes G major 7 and so on. Bm11 is a B minor 7 chord with the 11th (4th) note from a B natural minor (aeolian) scale added to it. This works fine in the key of A aeolian because Bm’s 11th is E, which of course is a note from the E aeolian scale. Adding any note from the key scale to a chord will just give you a jazzier sounding version of the same chord, and Bm11 is much easier to play than Bm7! The same goes for C major 13.
In bar four of the B part I have used a chromatic link from C maj 13 up to D7. Any time you have two chords in a progression whose roots are separated by a tone, you can create an ascending chromatic link between them by using a diminished or ½ diminished chord whose root note is on the semitone between the two original chords. In this case my progression goes Cmaj13 – C#1/2dim. – D7.
In the C part I have used a slightly unusual technique to create a “shimmery” sounding version on the part’s repeat. I replace chord I (Em7 in tetrad land) with chord IV from E dorian instead of E aeolian, aka A7. In this case I have left the top two open strings in the chord, to give me A9. This works well because the top two strings are B and E, the 5th and root of my key scale and adding any notes from the key scale to a jazzy chord will just give you an even jazzier version of the same chord. If you are playing a tune in the aeolian mode, you can often borrow chords from the dorian mode in order to give a moment of optimism to the tune. This works because Irish tunes in minor keys very rarely contain the sixth note of the scale, and it is this note which differentiates the dorian mode from the aeolian. In this case E aeolian should contain A minor 7 as its fourth chord, but I have used chord IV from E dorian, A7, instead! In dorian or aeolian you can always experiment with replacing chord I with chord IV from the other minor mode in order to create tension. If you are in the aeolian mode then dorian’s chord IV will sound bright and shimmery. If you are in the dorian mode then the aeolian chord IV will sound dark and regretful.