Music Theory: Chords, Scales, and Triads

Posted by Robinson Earle on Dec 11th 2020

As most humans are only capable of producing one note simultaneously, it’s safe to say that monophonic music came first. Over time, melodic threads were combined, creating the sort of sonic tapestry that can still be heard in isolated villages of Eastern Europe, and deep in the heart of the Ituri forest of the Congo. The throat singers of the Asian steppes succeeded in mapping the overtone structure inherent to the human voice. The Greeks adopted lyres and other instruments capable of polyphony into their musical theater. It was with Gregorian chant, however, that the concept of chord craft really took root.

A chord is a combination of two or more tones that is often, but not always, derived from a musical scale.

Musical Scales & Triads

Although pentatonic scales are clearly the oldest, the diatonic (7-note) Major scale functions as the theoretical starting point for much of western music. The initial Major triad in the key of C (C,E,G), which is formed by combining the root note with the first two non-unison overtones found within the harmonic series, is a natural place to begin.

A 7-note scale entails 7 corresponding triads that we can use to provide a harmonic backdrop.

Now, let’s consider all the triads implied by the C Major scale:

12345678 (1)
CDEFGABC

Skipping every other note, we produce the following:

CEG (I, C Major)
DFA (ii, A Minor)
EGB (iii, E Minor)
FAC (IV, F Major)
GBD (V, G Major)
ACE (vi, A Minor)
BFD (vii°)

Again, a Major triad is created by combining the root note with the first two, non-unison overtones that it produces. In the context of a diatonic Major scale, this would be the 1st, 3rd, and 5th degrees: C, E, and G.

Creating Minor Triads & Diminished Chords

To create a minor triad (relative to a Major), you lower the 3rd degree by a semitone, or half step. For example, if an E Major triad is E, G#, B, then an E minor triad would be E, G, B.

In a C Major scale, the ii, iii, and vi chords are minor.

To create a diminished triad, you lower the 3rd and 5th degrees by a half-step. If a B Major Chord is B, F#, D#, then a B diminished chord is B, F, D

In a C Major Scale, the vii° chord is diminished

Diminished chords have a pleading quality, and beg to be resolved.

Beyond the spelling of triads, there are many natural tendencies that we take for granted within a Major scale. Harmonic and melodic progressions are far from random.

For example, besides the root, the 5th scale degree exerts the most gravitational pull, followed by the 3rd.

The 2nd wants to return to the root, or jump to the 5th.

The 4th bears a special relationship to the root, as the root is its 5th ( CEG. . .FAC). As a result, it has a maternal quality. That’s why Sus4 chords sound so comforting.

The 6th is the relative minor of the root. The natural minor scale generated from the 6th will include all the same notes as the Major scale built on the 1, albeit with a different sequence, or starting point (C Major: CDEFGABC contains all the same notes as A minor: ABCDEFGA). The 6th tends to impart a sense of emotional conflict.

The 7th is desperate to ascend to the octave.

These tendencies vary amongst different scales, but some of the relationships, such as the relationship between the 1st and the 5th, remain intact. It is very rare for any human music to not include some form of 5th, mel

Complex Guitar Chordsodically or harmonically. Two examples would be the Raga Malkauns and the Locrian mode, both of which conjure feelings of overwhelming expectancy.

Now let’s move beyond the triads and the Major scale to define some more complex chords on the guitar.

C Major9

C Major9 is created by combining the Major triad with the 7th degree of the scale, and the 2nd degree of the scale in a higher octave: C, G, B, D, E. To my ear, it has a friendly, yet mysterious sound.

C 9

D m6

Ah, the Minor 6th. In this case, a D minor 6th making use of the open fourth string of a guitar in standard tuning. From the starting point of a Major triad, a Minor 6th flats the 3rd and adds the sixth degree of the scale, which for a D chord, would be the B natural. Minor 6th chords have spooky, yet alluring quality. They are exotic, yet strangely familiar. For reference, a Minor 6th is the foundational chord of the Jungle Book Overture.

D m69

A Minor 69 adds the 6 and the 9 (a 2 in a higher register) to a minor triad. This D m69 seems to pose a complex question. It pulls in different directions, enhancing its flexibility.

E m13

This E Minor13 contributes a six in a higher octave to the E Minor triad. The result is both softening and obfuscating.

E m6 add4

This E Minor 6 add4 is loaded with inquiry. It features the 6th and 4th degrees of the E minor scale on the fifth and fourth strings, and an Em triad on the top three strings. Lay all that on top of the rich open E string in the bass, and you’ve got quite a chord.

F maj7#11

Also known as a the “Lydian” chord, a Major 7 #11 simultaneously sounds modern and ancient. The Lydian mode only differs from the Major scale on one note, the #4, which is curiously also one of the earlier overtones found within the tonic’s harmonic series. The Lydian chord adds that #4 in a higher octave, making it a #11. With the Major triad, Natural 7, and #11 combined, you get five of the seven notes contained within the Lydian scale.

F maj13

To me, this is a very maternal sounding chord. In addition to the root, it includes a natural 7, two 5ths, a 9, and a 13. The softness of a Major7 enhanced by the tenderness of a 2 and a 4, albeit an octave up. Remember that the 1 is the 5th of the 4. In other words, the 4 is the mother of the 1.

G 13

This very adult chord sounds like a threshold that I wouldn’t mind dwelling in for a while. It’s a cozy, liminal space. The fifth string can be muted to make it movable, but as a G, the open A functions as an additional 9. The flat 7, 9 (2), and 13 (6) lend this chord a lovely inertia, but it still plays nicely with other dominant 7th chords.

G 13#11

This idiosyncratic combination of notes came to be known as the “mystic”, or “Prometheus”, chord by way of the Russian composer Alexander Scriabin, who had a profound interest in early 20th century spiritualism. In Scriabin’s words, it “was designed to afford instant apprehension of -that is, to reveal- what was in essence beyond the mind of man to conceptualize. Its preternatural stillness was a gnostic intimation of a hidden otherness.” He also referred to it as the “chord of plemora”, plemora being a Gnostic Christian term for the totality of divine powers. The above G 13 #11 is a transposition for the guitar, as Scriabin originally conceived of its voicing as C, F♯, B♭, E, A, D. Despite its awesome dissonance, this chord is actually based on some of the higher overtones in the harmonic series. Beyond its original context, Duke Ellington was able to find a place for the mystic chord within his 1958 piano piece, “Reflections in D”.

G sus4/D

By substituting a 4 for the Major 3rd, we create a magically expectant sus4 chord. Of course, by placing the 5 in the bass, this could also be interpreted as a D7 Sus4, or a C Sus2/D. It’s ambiguity is its strength, as this chord can serve a variety of harmonic functions.

A m11

We need only include the A on the open 5th string to render the previous shape an Am11. The two 11s (4ths) mitigate the sassiness of the b7 with “Sus4-iness”.

A madd9

This is one of my favorite guitar chords. There’s something rich and intriguing about its voicing. Must be all those open strings and the surprising way it arpeggiates. You can also use the open E on the low sixth string if you want to try alternating the bass. I have many compositions that employ this chord, and I also use it in my arrangement of the Jazz standard, Nature Boy.

A m7

Now trade the open B for a G (b7, eighth fret) on the 2nd string and you get a lovely minor 7th chord!

B dim7

Adding a diminished 7th to a diminished triad gives it an extra leg to stand on, improving its versatility. This Bdim7 resolves beautifully into C Major. Note that the diminished 7th degree is expressed as “double flat” (bb7), making it equivalent to the natural 6th degree of the scale. From Baroque operas to vintage cartoons, diminished 7th chords have been used to convey impending danger.

B 11 add b2

Here’s another interesting extended chord with limited application! Jokes aside, there is definitely melodic (if not harmonic) potential contained within this one. The addition of the b2 creates a fertile tension reminiscent of the Phrygian mode. Nothing like a semi-tone around the root to make you feel a pull towards home.

B dim7

This is one of my favorite movable shapes. Shift it up and down the neck chromatically and hear it sprout new roots. I think of this chord as a portal into other worlds.

Now that we’ve established a strange new vocabulary, let’s put these harmonic oddities to the test in the form of a novel progression: