Basics of Harmonization

By understanding the concept of “shell”, you’ve come to grasp the relationship between chord and melody. Now, I’d like to delve into the theoretical understanding of how to reinforce a melody by harmonizing it with sub-melody.

When it comes to adding harmony to the main melody, there are several styles possible. However, this time, I’ll focus on the most common approach in popular music: altering only the pitch while keeping rhythm and lyrics in harmony with the melody.

1. Parity and Harmony of the Shell

When discussing harmony, a key element is the “shell.” Acquiring the concept of the shell makes discussions on harmonization a lot clearer.

In the first part of Chapter.II, we confirmed that “odd-degree shells decrease tendency, making it easier for notes to sustain” and “even-degree shells increase tendency, making it harder to sustain.” We also noted that “the 7th degree has a bit more richness compared to other odd-degree shells.”

As the second line harmonizing the main melody is a “sub-melody,” such theory naturally applies.
Just as with the main melody, it is desirable to pay attention to the parity (=odd or even) of essential notes such as long ones, high-pitched ones, or the ones on chord changes. The combination of the parity of the main melody and harmony can be thought of in four different ways.

Summarized in a table, it would look like the following:

In simple terms, it can be summarized: The safety measure is to keep the essential parts of sub melody odd-numbered shell. The condition of “double instability” like ④ can still be utilized as an expression of musical idea, but the state of “the main melody is calm but the sub is causing disturbance” like ② could potentially have negative effects so a good understanding for dissonance is required to make use of it.

First and foremost, you should take care of the parity of the sub melody as much as the main. That’s the starting line.

The Importance of the Kernel

Of course, aside from the shell, don’t forget the presence of the kernel. Everything studied so far in melodic theory applies to the sub-melody. Therefore, there might be some situations requiring a bit of additional attention especially to fa and ti, which are strong tendency notes. I’ll discuss this “horizontal” aspect a bit later.

2. Intervalic Classification

Separate from the stability of the sub-melody on its own, an important aspect unique to the sub-melody is, of course, the intervalic relationship with the main melody.

Basically, the sub-melody should adhere to an equal interval while following the up and down movements of the main melody.

If you think that sub-melodies must be selected from the chord tones, that’s not true. While it’s reassuring to use chord tones at prominent points, the priority is more about reinforcing the movement of the melody line and its contour. Therefore, the primary focus is to adhere to the melodic outline rather than the chord, as shown in the above score.

Occasionally, intervals are shifted in order to get stable sonority from vertical perspective, but the primary concern is determining a single basic interval.

Three Classes

In terms of intervals, it can be broadly classified into just three classes.

These are 2nd above/below, 3rd above/below, and 4th above/below. And each class has distinct sonic characteristics based on frequency ratios.

Harmony’s textural qualities are often described as “soft” or “firm”. The interpretation of these subtle nuances may vary among individuals tho.

Intervals larger than 4th

Concerning intervals 5th and above, these can be obtained by shifting an octave of the previously mentioned intervals.

Consider 7^th as a variation of 2^nd, 6^th as that of 3^rd, and 5^th as that of the 4^th. Although they are not exactly the same, starting by memorizing these as “three classes” can provide a clearer perspective.

For instance, if you initially attempt to harmonize with a sub-melody 3rd above but it was too high to sing, lowering it by an octave will change the intervals to “6th below”. The intervalic structure is changed, but as it’s just an octave-based shift, certain quality of “softness” inherent in 3^rd harmony is still kept to some extent!

Tritone

One thing to be noted: When the pair is “fa and ti” (6 semitones), it is a very strong dissonant interval called a Tritone¹.

Though fa–ti is a 4^th interval and ti–fa is a 5^th interval, they’re totally different from normal 4^th/5^th. Consider they have a peculliar dissonance and should be handled with care. In this article, the word “4th” and “5th” are basically referred to as the normal intervals, not these tritones.

Moreover, with “quality changes” or accidentals, tritones can occur with notes other than “fa–ti,” so these instances require particular attention too.