Chord Basics for Playing the Harmonica
The chords played on guitar and piano that accompany a melody are built from intervals. As a harmonica player, knowing a little about chords can help you understand how the notes you play relate to the chord sequences used in the songs you play and can also help you understand written music.
The simplest type of chord has three notes and is called a triad.
The root of the triad is the note you start from. A C triad, for instance, is built up from C.
The third of the triad is a third up from the root. A C triad has E as the third.
The fifth of the triad is a fifth up from the root (it’s also a third up from the third of the triad). The fifth of a C triad is G.
Any consecutive chain of thirds can be a triad: C-E-G, E-G-B, G-B-D, B-D-F, D-F-A, F-A-C, A-C-E. You can find several of these in the note layout of a C-harmonica.
The blow notes are all C, E, and G — a C triad.
The draw notes contain three triads:
A G triad (G-B-D) in Holes 1, 2, 3, and 4
A B triad (B-D-F) in Holes 3, 4, and 5 and in Holes 7, 8, and 9
A D triad (D-F-A) in Holes 4, 5, and 6 and in Holes 8, 9, and 10
You can build a chord on any degree of a scale, using the notes of the scale. You use Roman numerals to number the chord according to the degree of the scale you use to build the chord. In the C scale, the first degree of the scale is C, so a C chord would be a I chord, a D chord would be a II chord, and so on.
Four basic types of chords
Four types of triads exist, each with different interval qualities:
A major triad has a major third and a perfect fifth. Your C-harmonica has two major triads: the C major triad formed by the blow notes anywhere on the harp and the G major triad in Draw 1 through 4.
A minor triad has a minor third and a perfect fifth. Your C-harmonica has one minor triad in two places: the D minor triad in Draw 4, 5, and 6 and in Draw 8, 9, and 10.
A diminished triad has a minor third and a diminished fifth. Your C-harmonica has one diminished triad in two places: the B diminished triad in Draw 3, 4, and 5 and again in Draw 7, 8, and 9.
An augmented triad has a major third and an augmented fifth. Your C-harmonica doesn’t have any built-in augmented triads.
Adding notes to basic triads
You can add any notes to a triad that sound good. For instance, you can add the 6th to a major triad to get a major 6th chord.
An often-used method for extending chords is to keep counting up the odd-numbered scale degrees and adding thirds to the chord. If a basic triad is 1, 3, and 5, you can add 7, 9, 11, and even 13 to the chord.
Note that 9, 11, and 13 are compound intervals — intervals bigger than an octave. The 9th degree is just the 2nd degree an octave higher, while the 11th is the 4th degree and the 13th is the 6th. Numbering them in an ascending line of numbers helps to clarify the method for creating them.
The diatonic harmonica in C includes a few extended chords:
A G major chord (Draw 2, 3, and 4) that extends to a 7th chord (by adding Draw 5) and a 9th chord (by adding Draw 6)
A B diminished triad with an added 7th (Draw 3, 4, 5, and 6)
A D minor 6th chord (Draw 4, 5, 6, and 7)
Most songs are accompanied by chords played on guitars, keyboards, or several instruments playing notes that add up to chords. Some songs just stay on one chord, but most include a sequence of chords called a chord progression. Each chord is played for a set number of beats or bars.
On sheet music you can see the names of chords written above the melody, sometimes with chord fingering diagrams for guitar. However, musicians often describe chord progressions by the relationships among the chords.
They do this by assigning the Roman numeral I to the chord built on the tonic and then numbering the scale degrees and using the Roman numeral for each scale degree to name the chord built on that degree.
When you name chords by relationships, you can switch from one key to another more easily than if you had to translate each letter name to the new key. If you know what those translate into in any specific key, you can just plug in the new values whenever you switch keys. It’s the mental equivalent of picking up a harmonica in the key of the tune you’re playing.
The most important chords in any key are the I chord, the IV, and the V. You may have heard people refer to simple tunes as being “just a I-IV-V progression.” They usually mean that the only chords used are I, IV, and V, but the chords may occur in some other sequence than I, then IV, then V.
The II, III, and VI chords may also occur in tunes, and sometimes other chords may be used as well.
In a major key, the I, IV, and V chords are usually major chords, while the II, III, and VI are minor. Minor keys are less consistent, but the I and IV are usually minor and the III and VI are usually major.
You can get more detail on chord types and chord progressions by reading up on functional harmony in a book on music theory.