We tend to focus on learning scales most of the time, but it can be very useful to look at chord forms as an alternative. Chords give a song a recognizable structure and a platform to improvise over. Chords, like scales, have particular formulas which can lend themselves nicely to the layout of the harmonica. Venturing into the world of jazz you may even find chord substitutions that work in the context of a song.
There are very few chords that can be played as we normally think of chords (a bunch of notes played simultaneously) that work on the harp. However, we can play a number of chords if we play the notes in sequence, also known as an arpeggio. In the context of standard blues, we can play the single notes of the chord the band is playing to stay in synch and at the same time break out of the standard scales for a key. In the section below I will chart out the common blues chords as they relate to the C harmonica.
Notes on Notation
In the charts below you will see the Roman numeral notation used instead of the actual notes. These are the scale degrees or intervals based on the key being played. When it comes to the harmonica, they are more useful because the scales maintain their patterns regardless of the key harmonica being played. Here are some basic chord formulations and their feels. Note that in blues you will frequently hear the I7 , the IV7 and the V7 . These are dominant 7th chords that provide a bit of tension and movement to the next chord.
Main triad notes will be in Green. Blue notes included in the chord will be in Blue and some extensions of the chord will be in Yellow
About the 9th and 11th
In some of the diagrams below I show the 9th and 11th degree as IX and XI. These notes help extend and color the 7th chords and expose more notes - they are getting further from the main chord and are usually more for spice than the main notes.
When we are playing the blues , particularly standard progressions, there are only a few chords that form the foundation of the chord progression - the I,IV and V chords. While these form the basis of the blues chords it is more common to find the dominant 7 chord being played. This chord has a slightly unsettled feel that helps move the song to the next chord. If you are looking at something like guitar tabs, or many of the backing tracks, you will see this expressed as I7 , IV7 and V7 or by the specific chord being played - G7, C7 and D7.
Chord Type
Major
Minor
7th
Minor 7th
Major 7th
9th 11th 13th
Formula
I III V
I IIIb V
I III V VIIb
I IIIb V VIIb
I III V VII
I III V VIIb IX (ii) XI (IV) XIII(VI)
Notes
The major chord, solid sounding
Sad, dark - The flat III is the important note here.
Dominant 7 - unsettled, moving to another chord.
Minor Dom 7 - unsettled, moving to another chord.
upbeat but not edgy.
These are extensions of the 7th chord. The notes here 'fit' but are not very 'solid', meaning you can play them over a 7th chord but you won't want to linger on those notes most of the time. The 9th is the same note as the ii note, the 11th is the same as the IV note and the XIII is the same as the VI.
Second position on the harmonica means we are playing in the key of G on the C harmonica. Below are the layouts for the most common blues chords.
The major chord - I,III, V are colored in Green - these are the main notes that define the major chords. The VIIb helps define the I7 chord sound and is also on the blues scale, shown in blue. The 9th, 11th and 13 (ii, IV and VI) are colored in yellow. You can see from this layout that there are many notes available, which is another reason why we often play in second position!
The major chord - I,III, V are colored in Green - these are the main notes that define the major chords. The VIIb helps define the I7 chord sound and is also on the blues scale, shown in blue. You will need to learn some bending to get to the VIIb. The 9th, 11th and 13 (ii, IV and VI) are colored in yellow and there are many available. It is advisable to stay away from the VII ( hole 3 and 7 draw).
The major chord - I,III, V are colored in Green - these are the main notes that define the major chords. The VIIb helps define the I7 chord sound and is also on the blues scale, shown in blue. The 9th, 11th and 13 (ii, IV and VI) are colored in yellow and there are many available. It is pretty hard to get to the III note on the major chord , but the IIIb note is in the blues scale
Suggestions for Chord Arpeggio Practice
1) Try playing the I,III,V notes for each chord - this is called the 'major triad' . This is tricky for the V chord!
2) Try playing as much as you can of the 7th, 11th and 13th chords notes.
3) Take a lick built on one chord and try to make it work on the other chords.
The classic 'Juke' lick from Little Walter is usually tabbed out as 2 3 4 5+ 6+ . This translates to I III V XIII I . If you move this to the IV chord ( C ) you can play the same lick using 4+ 5+ 6+ 6 7+ ! Taking this to the V chord (D) , it gets a little harder because it is hard to get to the III unless you bend the 2 draw. This is a very good bending practice on the low notes 1 2' 3'' 3 4 . Or you could cheat a little and use the IIIb and play 4 5 6 7 8
You could also play the same lick over each chord in the progression and see how its nature changes depending on the chord being played in the song. This is actually done in the song. Again using the Juke lick. 2 3 4 5+ 6+
Over the I chord (G) the lick is I III V XII I Over the IV chord (C) the same notes are V VII IX V . When we get to the V chord this will sound like XI XIII I IX XI . Note how the lick sounds different because of its relationship to the underlying chord.