You’ve memorized some chord shapes, but don’t understand the theory behind their construction or how to transpose, invert, or modify them.
Start by gaining a grasp of chord theory, and then apply that knowledge to the fretboard.
We often start our journey on guitar by learning the basic open chords, and why not? The guitar is a wonderfully flexible instrument that allows for full, rich harmonies with easy fingerings. Yet so many guitarists stop there. They memorize a handful of shapes, maybe a few barre chords, and rob themselves of boundless options right under their fingertips. As in all lessons in this series, we will aim to dismantle a limitation by building a strong foundation of understanding.
Full disclosure: This is a dense lesson. If you’ve been keeping up with this series and made it this far, you’ll be well equipped. But don’t be afraid to take a little extra time to digest the concepts.
Understand the Building Blocks on the Staff
Before we examine chord construction, we first need to take a look at intervals, the distances between notes and the building blocks of chords. Harmonic intervals are notes played simultaneously, and melodic intervals are notes played in succession. Intervals are made up of two parts—a numeric distance and a preceding modifier. The numeric portion can be a unison, a second, third, fourth, fifth, sixth, seventh, or octave (Example 1). Any given interval has one of five qualities, with abbreviations shown in parentheses: perfect (P), major (M), minor (m), augmented (+), and diminished (º).
Let’s use the familiar major and natural minor scales as a basis for seeing intervals in context, upwards from the root in the keys of C major (Example 2) and C minor (Example 3). Notice that the perfect intervals are the same in both the major and minor modes: unison (P1), perfect fourth (P4), perfect fifth (P5), and octave (P8). If you raise a perfect interval by a half step, it becomes augmented, for example C–G# (+5). And if you lower a perfect interval by a half step, it becomes diminished, as C–Gb (º5).
The major and minor intervals are the second, third, sixth, and seventh. Both major and minor scales have a major 2nd (M2) between the root and the second scale degree. The third, sixth, and seventh are the notes that differ. A minor interval compressed by a half step becomes diminished, and a major interval expanded by a half step becomes augmented. That means that in addition to building a minor scale from the pattern of half and whole steps, you can form it by taking the major scale and lowering the third, sixth, and seventh scale degrees a half step. A minor interval lowered by a half step becomes diminished, while a major interval raised by a half step becomes augmented.
All intervals have levels of consonance or dissonance, musical rest or tension, respectively. The perfect consonances—the unison, P5, P8—have the least tension. Imperfect consonances are major and minor third and sixth. The P4 is a bit of a hybrid—context determines if we hear it as consonant or mildly dissonant. The M2 and m7 are mild dissonances, and the m2, M7, and tritone are strong dissonances. The tritone (or +4/º5) divides an octave in half. (It’s also the blue note in a minor blues scale, as you may remember from the previous lesson.)
Intervals can be inverted—the top and bottom note switching places, as shown in Example 4. A way to quickly calculate the new interval is to subtract the original interval from the number nine and flip the quality—major becomes minor (and vice versa), perfect remains perfect, and augmented becomes diminished (and vice versa). So a m2 becomes a M7 (9 – 2 = 7; minor becomes major).
Build Some Triads
Now let’s examine chords in their fundamental form, triads, made up of three notes—
a root, a third, and a fifth. A triad can be major, minor, augmented, or diminished, and its intervallic structure determines which (Example 5). A major triad has a M3 and a P5 above the root. A minor triad has a m3 and a P5. An augmented triad has a M3 and an +5. A diminished triad has a m3 and a º5.
Put this to practical use by forming various triads with C as the root. First write out the C major scale, as in Example 6. Find the major third above the root. Take a moment to see it both as the third degree of the C major scale and as an interval: a M3 is two whole steps—C, whole step up to D, whole step up to E, our major third. Now we need our fifth. Scale degree 5 in a major (or minor) scale is a P5 up from the root. That gives us G as the fifth. Considering it in terms of intervals, a P5 is M3 + m3 (or m3 + M3). So our C major triad is: C–E–G.
Let’s transform the C triad to minor: C, a whole step up, to D, and an additional half step to Eb. We still need a P5, so our C minor triad is C–Eb–G. Notice that the only note that C major and C minor triads don’t share is the third? We still need a P5 for minor, so our C minor triad is C, Eb, G. Notice how the only note that major and minor don’t share is the 3rd? That’s why it’s often said that the third determines a chord’s quality.
Augmented and diminished chords are one more step: To get a triad augmented, take a major triad and raise the 5th a half step: C, E, G#. To get a diminished triad, take a minor triad and lower the 5th by a half step: C, Eb, Gb.
Take It to the Fretboard
For Example 7a, locate a C on the low E string. Then find the major third (E) on the A string and the (G) on the D string. C major! Next, lower the third a half step to transform it to C minor, as shown in Example 7b. Lower the fifth a half step, to Gb, to form a C diminished chord (Example 7c). For Example 7d, revert to the C major triad and raise the fifth a half step, to G#, to form C augmented.
Going a step further, let’s work our way up the neck finding C major chords, using the four highest strings and doubling whichever chord tone is most practical in any given position. In Example 8, starting in the open position, as our top note we have an open E, the third of C major. Then go to the B string and find another chord tone, in this case, C. The open G is the fifth, and if you fret the E on the D string, you’ll see a familiar open chord (minus the C you’re probably used to playing on the A string). Continue by moving up the fretboard, finding chord tones, while keeping notes in common when possible. Notice how they connect and invert, all forming C major chords, but with the notes stacked in various ways. You’ll need to use your knowledge of the fretboard to be aware of which notes are which.
Your assignment, one that will be enormously helpful, but will require your full engagement: Take these C major chord forms, or voicings, and convert them to minor—remember, just find all the thirds (in this case, E), and lower them a half step to Eb. Come up with comfortable fingerings. Then try to memorize the shapes, but only after you really know which note is which, both in terms of pitch and its role in the triad. Then try both major and minor in other keys.
Good luck, and have patience! Your future self with great chord fluency will thank you.
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This article originally appeared in the March/April 2019 issue of Acoustic Guitar magazine.