This classic 5 part slip jig is in the key of E aeolian. That means that the chords available are E minor, F# diminished, G major, A minor, B minor, C major and D major.
I have broken the A part down into chord I and chord V sections. There are no sections which particularly sound like they need chord IV in this part. Instead of using B minor, which is hard to play for beginners, I have replaced chord V with its related major, D. Slip jigs are built with three foot taps per bar, and you would usually expect to find chord V on every sixth foot tap. In this case these sections take D (chord VII), as a substitute for B minor (chord V).
In bar four I have broken up the sea of E minor by replacing it with its related major, G major.
The tune’s B part has very clearly switched from E aeolian to G ionian. Both of these modes contain the same notes, but you can feel that the switch has taken place because the first bar of this part goes “B D B A G F# G – – “. The long G at the end makes the bar feel decidedly G-ish, there is another G in the bar and not an E in sight. G major’s chord V is D, so that goes on every sixth foot tap.
The C and D parts are harmonically remarkably similar to the A part but an octave higher…
And the E part is very similar to the B part, switching back to G ionian.
In this version of the A part I have followed the melody of the first bar with the bass notes of my chords. The melody goes “E D E F# E F# G – F#”. I have followed this with the chords Em, D/F# and G. The D/F# chord is D in the first inversion. This is the standard way of avoiding the diminished chord in any folky key- play the first inversion of the chord whose root is two below that of the diminished chord in the key scale. In this case chord II in the key of E aeolian should be F# diminished, and I avoid it by playing D in the first inversion (because D is two notes behind F# in the key scale; D – E – F#). A D chord contains the notes D, F# and A, so in its first inversion it has the F# at the bottom. You can play this shape by making a D chord and adding the thumb on the second fret of the bottom E string. This shape is shown below.
I have used the actual chord V in this version’s second bar. In the fourth bar I have replaced E minor with its related major for a bit of light relief. As I have used one related major, I like to follow up with another (if I’ve lightened the tone I like to stay light until the next V-I at the end of a section). For this reason I follow it up with D (chord V’s related major) instead of the darker chord V.
In the B part I have created a sense of movement in the first G section by switching between G – D/F# – G. This works well because the bar contains the notes “B D B A G F# G – D”. If you think of the bar as containing three potential chords, then the second block, A G F#, would be outlining a chord V section, or its related major D (D major contains the notes D, F# and A, two of which are in this section). The Am chord in bar two works well because the section ends on an A. I have not done this in bar four as that would end a section without a chord V, a travesty if ever there was one (also because that bar ends not on an A but on a D).
In the C part, I have used an A minor (chord IV) in a similar way at the end of the second bar to create an unfinished feeling to the section. Again, I have reverted to the more standard D to finish the section off.
In the C part I have used a D/F# to create a nice linking bassline between Em – G. I have used it both ascending in bar three of the C part and descending in bar 4. It is fine to use D/F# in the chord V section as it is an inversion of chord VII (still functionally chord VII) which is chord V’s related major.
In this version I have replaced some of the triads (three note chords eg Em, G, C etc) with their equivalent tetrads. You can replace any minor chord with a minor 7, eg the B minor 7 in bar 2 of the A part, the A minor 7 in bar 2 of the B part or the E minor 7 in the C part. As E aeolian contains the same notes and therefore chord options as G ionian, the complete list of tetrads available would be E minor 7, F# ½ diminished (we will avoid this by using D/F#), G major 7, A minor 7, B minor 7, C major 7 and D7.
In the second half of the C part I have also used a C major 9 chord. This works because so long as you are building on top of the right kind of tetrad, you can add any notes from the key scale to get an even jazzier sounding chord which will sound fine in context. In the case I have added the 9th note relevant to C (aka the second note played an octave up, so D). This works fine because a D note is within the scale of E aeolian.
In the second time through the B part I have replaced G major with its related minor E minor, and that in turn has been played as a tetrad giving E minor 7. I follow this with B minor 7, another substitute for G major. You can substitute any major chord for the minor whose root is two notes below it in the key scale (its related minor, in this case E minor 7), or that whose root is two notes above it in the key scale (in this case Bm7).
The final chord in the tune is an altered dominant. These are dominant seven chords also containing altered notes from outside the key scale. These can only be used when you are about to resolve down a fifth, in this case from chord V to chord I. They create lots of tension but so long as you resolve down a fifth they sound great!