Understand Chords: Chords In Keys (Part Two of a Series)

In Part One, we learned about “tertian harmony,” the most common way of building chords, and how “triads” are built around the interval of a “third,” consisting of three tones, “root,” “third,” and “fifth.”  Finally, we learned that triads come in four basic flavors or “qualities”—in order of  frequency of use they are major, minor, diminished and augmented.

As hinted in Part One, there are other types of chords, both tertian and non-tertian.  But before delving into them, let’s look at how triads can be used in ordinary music.

In Example 1 we see the seven triads you can build using the tones of the “A natural minor” scale. Two common ways of labeling the triads are shown; both work the same way: the triads are assigned a number according to which scale degree forms their root. ('Scale degree' refers to the position of a particular pitch in a particular scale; for instance, in C major (shown), "C" is scale degree one.) In “Nashville Notation,” the number is a plain Arabic numeral; in more academic settings a Roman numeral is used, but the meaning is the same either way. (Though the Roman numeral analysis usually includes information about the chord quality--see how the major triad numerals are upper-case, while the minors are lower-case?)

Note how the chords labeled 1, 4 and 5 are all minor triads, while 3, 6 and 7 are major; 2 is the lone diminished triad, and there are no augmented triads. 1, 4 and 5 are often called the “primary” triads of a key because they best define the sound of a key and are therefore the triads most often use.

By the way, in Classical style--the style of Haydn, Mozart and Beethoven and their contemporaries--the usage of harmonies can sometimes be even more economical; it’s not that unusual to have significant stretches of music written with only the 1 and 5—or should I say, the I and V—triads.

Here’s an example of a chord pattern using the primary triads of our natural minor scale.

And here’s part of a Canadian folk melody that works well with the primary triad pattern above.

Notice how the main notes in the melody (circled) match the notes found in the chords accompanying them.

Most listeners will agree that this version has a very different sound—happier, perhaps, or warmer.  Here it is with the corresponding version of the same tune.

The mournful quality of the original is completely gone.  None of the primary triads in A minor are present, so our ears search instead for a key in which the chords we hear make “better sense.”

And they find it.  The same notes we have been working with so far can be heard with the tone “C” as scale degree 1—the tonic—of its own scale, C major.

Rewriting the scale to reflect this perception, we obtain this:

Notice how the three principal triads 1, 4 and 5 are now the three major triads. When Harlan Howard described the essentials of a good country song as “three chords and the truth,” it was I, IV and V that he had in mind.

But it’s not as if only country songs can be harmonized exclusively with primary triads. That’s true of a great many melodies. A few traditional examples:

“Happy Birthday”

“On Top Of Old Smoky”

“12-bar Blues”

So far all of our examples have used the notes of either the C major scale or the scale called its “relative minor,” A minor. Neither scale uses notes needing sharps or flats.

Unfortunately, this satisfyingly simple state of notation doesn’t always suffice. For various reasons, a tune may need to be pitched higher or lower; probably the Number One reason is to properly fit the range of a particular voice or instrument. For example:

Clearly, “Happy Birthday” for this voice needs to be somewhere in between the high and low versions we just heard.  We can achieve this by shifting our tonic to “G.”  Here’s how the resulting harmonized scale looks and sounds, using no sharps or flats:

This doesn’t sound bad, but it doesn't sound quite right either, and several chords have different qualities than their corresponding chords in the C major scale. 3, which should be minor, is diminished; 5, which should be major, is minor; and 7, which should be diminished is instead major. All these discrepancies can be fixed if we raise “F,” the seventh scale degree, halfway toward “G”—a tone sometimes called “G-flat” (written “Gb”) but more often “F-sharp,” or “F#.” By either name, it is played on piano by pressing the black key between “F” and “G.”

Applying this alteration throughout gives us the following scale--G major.

(Note the three places where F# is needed. Usually, instead of writing the sharp each time, a single sharp would be placed at the very beginning of the staff to indicate that F#, not F, is the “default” tone at that position in the scale. This is called a "key signature," and we'll learn more about them later.)

Let’s try “Happy Birthday” again, using the G major scale this time:

Not bad!

But suppose we want to try it just a bit lower.  We’ll move our tonic to F.  Here’s the scale that results:

Again, there are discrepancies from the pattern we expect.  Checking the chords, we find 2 to be major, not minor, 4 is diminished not major, and 7 is minor not diminished.  Once again a single note can be adjusted to fix these discrepancies.  This time, “B” must be lowered to “B-flat” (written out “Bb.”)  It is again a black key note on piano, and is found between A and B.

Let’s hear “Happy Birthday” in this 'new' key of F Major.

Again, workable.  And notice how the tone color of the guitar changes with the changes in key, too--each version has a slightly different "personality" in this respect as well!

But let’s step back and consider what we just did. We found two different ways to change C major to another major scale—first, by raising a single note, scale degree 4; and second, by lowering a different note, scale degree 7. Can we do the same thing with the F Major scale?

Yes—as shown, by lowering scale degree 7, E, to Eb, we created a new scale, Bb major.  And by raising scale degree 4, we transformed F “back” to C major.

These two processes can be repeated on any major scale.  We could raise scale degree 4 in G to create a new major scale, then raise its scale degree 4 to create still another, and so on.  Where does this process lead us—other than in possession of a lot of different major scales, that is?

But it turns out there is a tighter limit than that: considering guitar frets or piano keys from any note up to its octave, we find that there are only twelve distinct tones available to us. We may have fifteen names to assign, but we only have twelve notes to which to assign them.

Twelve tones can conveniently be arranged in a circular pattern, like that of a traditional analog clock or watch face, with the numbers arranged clockwise from one to twelve. At the top—the “12 o’clock” position—we could place our “C.” Clockwise one position would go our first “sharp scale,” G. Counterclockwise—11 “o’clock”—would be our first “flat scale,” F, and then, at “10 o’clock,” Bb. Following out this logic gives us this arrangement:

This useful arrangement is called the “circle of fifths” (or, sometimes, “fourths”—why, I will leave for another Hub.)  One of its useful properties is that any three adjacent places on the circle will give us the roots of the three primary triads of the scale whose tonic is found at the central position of the three.  That’s a mouthful, so consider a concrete example:  at the top of the circle we have C; the adjacent tones are F and G.  Sure enough, these are the roots of the primary triads in C major.  Or take A, at the 3 o’clock position:  D, its scale degree 4, is at 2 o’clock, while its 5, E, is at 4 o’clock.

If you can remember the circle, you can use it to quickly convert between scale names, like F major, and the names of the associated primary triads—something that can be quite handy.  “Happy Birthday in Eb?  Sure—I’ll just get my Ab and Bb chords ready!”

More importantly—if of less obvious immediate practicality—the circle of fifths provides a “map,” a means of organizing chords for songwriting or arranging purposes. Any chord can follow any chord today—but what does this or that particular sequence of chords mean?—that is, how does it “feel” as you listen to it? Is it smooth, shocking, warm or icy cold? One clue is how close two chords are “tonally”—do they belong to the same key? Or perhaps to one nearby on the circle of fifths?

As it stands, our circle doesn’t let us easily assess this for all chord qualities. But it is easy to expand. Each place on the “expanded” circle will list three triads: a major triad, as before; outside that ring a minor triad sharing two notes with it; and a diminished triad a half-step lower. ("Half-step" means the interval of one semitone--the distance of one fret or piano key.)

Of course, there are other factors that make a particular chord the exact “right” one for a particular moment—and we’ll discuss those in another Hub some day. For now, we’ve covered enough ground. We have:

--Related chord qualities to positions with major and minor scales;

--Explained “Nashville” and standard notation for chord labeling by scale degree;

--Defined “primary triads” and shown how they can be used to harmonize many melodies;

--Explored how and why different keys are needed, and how a scale can be transformed to obtain new scales and keys;

--Examined the circle of fifths as a “map” of tonality and a guide for chord selection and chord analysis.

Surely that’s lots for one day!