How Chords Work
People who play music are often analytical by nature. You’ve probably scrutinized recordings of music you wanted to learn, figuring out what tempo to take or how to smooth out the transition between the bridge and the chorus. Or maybe, at some point, you’ve had the urge to learn about the mechanics of your instrument—what exactly happens when your fingers hit the keys, or when your breath goes through the mouthpiece.
But some things in music are a little more difficult to explain in words. When you hear music that grabs you emotionally, it’s not so easy to put your finger on why you react to it. Though it may be hard to describe exactly why music has the power that it does, the ability to analyze chords helps to unravel the mystery. That’s because chords and chord progressions have a great deal to do with the character of music. Chord analysis, also known as “harmonic analysis,” is where the logical and emotional sides of music come together.
Explanation of Triads
When it comes to chords, three is a magic number. Since the 16th century, triads—groups of three different notes that are each a third apart—have been the most common harmonies found in Western music, both classical and popular. So, it’s important to be able to recognize triads in order to understand how and why chords work together the way they do. Before you can recognize triads in your music, you first need to know how they are built.
To form a major triad, start with any one pitch, the root, and add the note a major third (four half-steps) above. Then, add the note a minor third (three half-steps) above that. For example, a C major triad includes the notes C, E, and G.
The opposite order of intervals is used to form a minor triad: above the root is a minor third interval, and a major third “stacks” on top to complete the triad. So, the notes in a C minor triad are C, Eb, and G.
Notice that with both major and minor triads, the root note and the top note are always a perfect fifth (seven half-steps) apart. Whether the triad is major or minor all depends on the middle pitch.
Diminished triads use only minor third intervals, making the notes in a C diminished triad C, Eb, and Gb. Augmented triads, on the other hand, use only major third intervals. C, E, and G# make up a C augmented triad.
Do as the Romans Do
If you’ve played from lead sheets before, you’ve probably seen labels such as “C maj” or “CM” to indicate a C major chord. But while these types of symbols tell you what notes to play, they tell you nothing about the function of the chord. The thing is, chords have a chameleon-like nature: a C major triad that appears in a song in the key of C major acts differently, and has a different purpose, from a C major triad that appears in a song in the key of F major.
For this reason, when analyzing chords, it’s more helpful to use the Roman numeral labeling system. With this system, the chord is labeled with the Roman numeral that corresponds to the scale degree of the root note. So, in the key of C major, an F major triad is called a IV chord because F is the fourth scale degree, or the fourth note, in the C major scale. In the key of D major, the G major triad is the IV chord, and so on.
Major triads are represented by uppercase Roman numerals (e.g., VI), while minor triads are represented by lowercase Roman numerals (e.g., vi). A diminished triad is shown with a lowercase Roman numeral and a superscript circle (º) next to it. An augmented triad is notated with an uppercase Roman numeral followed by a superscript plus sign (+).
In any major key, the triads you are most likely to find are: I, ii, iii, IV, V, vi, and viiº. In a minor key, the most common triads are: i, iiº, III+, iv, V, VI, and viiº. Below, these triads are shown in the keys of C major and A minor.
In both major and minor keys, I (or i) and V chords sound the most stable to our ears. This explains why many songs and pieces end with a V chord followed by a I (i) chord: this chord change makes the music sound final and resolved.
Get to the Root of the Chord
One more thing to keep in mind with triads is that the notes don’t always stack up in the “right” order. When the root note is on the bottom and the thirds are stacked above it, this is called “root position.” However, if the same notes appear in a different order, and even in different octaves, this is called an “inversion.”
In the examples below, you’ll find that, although each chord looks different, they are all made up of the same notes—C, E, and G—so if you were to label these chords in a harmonic analysis, you would use the same Roman numeral for each. (There are superscripts that can be used to distinguish inversions, but for now, stick to the basic Roman numerals.)
Now, to get to the root of things (no pun intended!) and discover why we bother labeling chords, follow this harmonic analysis of the triads found in Pachelbel’s Canon in D major. Note: the chords have all been arranged in root position here.
Many people put this famous canon at the top of their lists of favorite classical pieces and its chord progression is also found in countless popular songs. So what makes Pachelbel’s progression work so well?
Harmonic analysis reveals the fact that chords create the same pattern that you would find in any good story: an introduction, a conflict, and a resolution. The strong and stable I and V chords introduce the key as D major. The minor chords that follow, vi and iii, are weaker to our ears, so they present the “conflict.” This tension begins to ease with the appearance of the more stable IV chord, and all conflict is then resolved when the V chord leads back to the final I chord.
The next time a song or piece catches your attention, get your hands on the sheet music and take a look at the chord progressions. Do you notice any patterns, such as where certain chords tend to lead, or what types of chord changes trigger your emotions? You’ll find that a little curiosity goes a long way in discovering the reasons behind music’s expressive powers.