Let's move on to another aspect of melodic harmonization that doesn't have to do with harmony. Think of a few recent musical acts that use harmony: Simon and Garfunkel, the Indigo Girls, and the Beatles. These groups use true melodic harmony: notes that sound consonant with each other. You've no doubt heard some bad attempts at harmony, usually at holiday parties after a few glasses of spiked eggnog. Someone tries to sing a second part to “Silent Night” or some other tune. The result is usually less than desirable.

It's important to have a general idea of what notes work when harmonizing single-line melodies. This is how chords evolved. Gregorian chant started with a single line of music, called monophony. As time went on, a second voice was added. Limited intervals were allowed, usually fourths and fifths (hence they are called perfect). Over many hundreds of years, a system of harmony built on thirds evolved. This system, known as tertian harmony, has been the focus of this book because it is the basic formula for harmony. Since tertian has as its root tertiary or three, thirds are a great place to start.

One Third Fits All

The first place to look is thirds. Simply put, you can spot harmonize any melody by harmonizing a diatonic third above the original melody.

The diatonic part is key here. You can't just play any third (major or minor), you have to know what key the melody is in and play the notes that fit with it. FIGURE 11.8 gives a very simple example in D major.

FIGURE 11.8 Melody Waiting to Be Harmonized

To harmonize this melody, start a second part, three notes up in the D major scale, and follow the contour of the original melody. The result is shown in FIGURE 11.9.

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FIGURE 11.9 Melody Harmonized in Thirds

Inverse

The inverse of a third is a sixth, and a sixth is another very nice way to harmonize a melody. Typically, you'd harmonize a sixth down, diatonically. This brings you to the same notes that you had when you went a third up. The difference is that the harmony is now below the original melody note. Both approaches work well. Check out the first example, this time with parallel diatonic sixth harmony, in FIGURE 11.10.

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FIGURE 11.10 Same Melody, Harmonized a Sixth Below

Both sound quite nice.

Intervals You Can Use

When harmonizing, certain intervals work almost all the time, and others are very hard to use. Here is a list of the intervals by type. Remember that when you are harmonizing melodies in keys, think diatonically for the melody notes.

• Unison/Octave. Not really a harmony per se, but the effect of doubling a melody can be a nice way to add some textures.

• Seconds. Seconds verge on the edge of tension and dissonance and should be handled with care. They can work at certain points in a harmony for some color, but you'll rarely find more than one in a row; you can forget parallelism.

• Thirds. You can't go wrong with thirds. They just always sound nice. They work great in parallel, too.

• Fourths. Fourths can be nice, but not in parallel. Parallel fourths are one of the major no-no rules of voice leading. However, since there is a fourth interval from the fifth of a triad to the root, a fourth can be just the right interval.

• Fifths. Fifths are also consonant intervals that work well. You don't want them in parallels either as they break the other major rule of voice leading. Plus, if you harmonize with straight parallel fifths, it will sound like Gregorian chant.

• Sixths. Sixths are the inverse of thirds. Sixths also always sound very good all the time. They work in almost all situations, especially in parallel motion.

• Sevenths. They are another dissonant/tense interval. They may work at certain points, but in general, sevenths won't sound consonant. You're also rarely, if ever, going to see them in succession one after another.

In general, the tense intervals, the seconds and sevenths, are not something to avoid. A bit of tension and release is what music is built on, so using those intervals sparingly may add just the perfect color to your music.