12.1 Introduction

Consider the following excerpts and in each case take note of the interaction that occurs between the melodies of the individual parts:

Example 12–1 is taken from a sixteenth century vocal composition by Orlande de Lassus. It begins with a single voice. When the second voice joins, three bars later, it imitates the melody heard at the beginning. As the piece progresses, the two voices are heard winding around one another, trading ideas in a kind of musical conversation. The excerpt shown in Example 12–2 comes from a string quartet by Halina Krzyżanowska. It begins with the four instruments playing at the same time. In terms of rhythm and pitch, their parts move in and out of alignment as they cooperatively shape a pair of musical phrases. Although the excerpt shown Example 12–2 was written nearly three and a half centuries later and sounds remarkably different, we may observe that it follows the same guiding principle as the excerpt in Example 12–1. Like Lassus, Krzyżanowska weaves simultaneously sounding melodies together to form a complex but harmonious musical texture. This bringing together of multiple melodic voices is known as polyphony and for many musicians, composers, teachers, and scholars, it is the very foundation tonal Western art music.

It is important to note that melodies like those heard in the examples above are not combined haphazardly. In most polyphonic tonal music the composer takes great care to consider the various harmonic sonorities that occur as the melodies move forward together. These composers, then, strike a careful balance: on the one hand they want each individual melody to retain and project a sense of independence, on the other hand they want all of the melodies to blend together and create harmonic cohesion.

The purpose of this chapter is to familiarize you with the concept and handling of polyphony in tonal Western art music. Interval progressions—patterns of intervals played in succession—form the backbone of this particular style and a firm understanding of how they work will enhance your experience of the music you hear, perform, analyze, and create. This chapter will outline and describe a series of standard progressions. You may think of the list presented here as a basic catalog of polyphonic building blocks. We will begin our discussion of interval progressions by revisiting the concepts of consonance and dissonance. The remainder of the chapter will describe the different ways in which two voices might move in relation to one another and the various interval progressions that employ these types of motion. (In subsequent chapters you will be given an opportunity to expand these progressions by adding a third and fourth voice—see, for example, Chapter 14.)

12.2 Consonance and dissonance

For now, we will consider only consonant intervals: the perfect consonances (unison, perfect fifth, and perfect octave), and imperfect consonances (minor/major thirds and minor/major sixths).

We will not yet consider dissonant intervals (minor/major seconds, minor/major sevenths, augmented or diminished intervals) and so the following sonorities will for now be excluded:

Notice that one of the intervals in Example 12–4 is perfect. The perfect fourth (P4) is a special case. Although considered consonant by some definitions, it is traditionally treated as a dissonance in two-voice textures. When only two voices are present, they are not permitted to form a perfect fourth or any other dissonance.

12.3 Parallel motion

When two voices move simultaneously in the same direction, while keeping the intervallic distance between them constant, we say they are moving in parallel motion. This type of motion is common in Western polyphony, though with some regulation since it tends to diminish the perceived independence of the voices. Parallel motion is typically used only with certain intervals. The following progressions, for example, are quite common:

Note that we are not concerned with the exact quality of these imperfect consonances. The intervallic motion shown in Example 12–7, for example, is considered parallel even though it moves from a major third to a minor third.

Both of the progressions shown above also commonly appear in reverse:

These examples show the same standard interval progressions as those discussed above, but now with descending motion in both voices. The interval progressions outlined in the remainder of this chapter are similarly reversible and from this point on, each progression will be presented alongside the reversed version.

Parallel thirds and parallel sixths are consonant but also allow the listener to identify the individual voices. They are therefore ubiquitous in tonal Western art music. Voices forming perfect intervals (unison, fifth, octave), on the other hand, blend together so well that many practitioners feel they suppress the listener’s sense of differentiation among voices.

When pairs of voices maintain perfect intervals as they move up or down, a listener may begin to lose the sense that they are actually hearing more than one pitch at a time. In other words, the individual melodic voices risk losing their independence. In this style of music, then, parallel motion is strictly avoided between two voices forming a perfect interval. The following interval progressions, then, are almost always avoided in this style:

Although this chapter is concerned with consonant intervals only, it is here worth mentioning one interval progression that contains a dissonance. As mentioned above, parallel motion from one perfect fifth to another is not permissible in this style. Motion from a perfect fifth to a diminished fifth, on the other hand, is:

For reasons that will become clearer later on in Chapter 16, the interval progression shown in Example 12–17 is allowed in this style. Movement between these intervals in the opposite direction—where the perfect fifth arrives via stepwise motion in both voices—is considered forbidden and should be avoided in two-voice textures:

12.4 Contrary motion

When one melodic voice ascends while another descends, we say that the two voices are moving in contrary motion:

Many composers of early polyphonic music showed a preference for this type of motion since it projects a sense of melodic independence. The two voices—though singing together—maintain their own identity, leading to a richer, more interesting texture.

Because of the acoustic properties described above, the group of standard progressions involving parallel motion is relatively small. By contrast, the group of interval progressions where voices move in contrary motion is much larger. It will be helpful, then, to divide this group into three categories:

• Both voices move by step
• One voice moves by step, the other by leap
• Both voices move by leap

Both voices move by step

We will begin by looking at interval progressions where each voice moves by step in contrary motion. These progressions may start from a unison, a third or a sixth. In each case, the two voices begin with a consonant interval and move in opposite directions (contrary motion). A unison expands to a third, a third to a perfect fifth, and a sixth to an octave, as shown here.

Notice that there is no standard interval progression in which the voices expand outwards by step from a perfect fifth. If two voices forming a fifth were to move away from each other by step, the result would be a seventh, which is a dissonance and is not permitted here.

These interval progressions can also appear as compound intervals. The 1–3 interval progression shown in Example 12–15 (and reproduced in Example 12–18a), for example, can also be written as an octave followed by a tenth. In other words, the interval progressions shown in Example 12–18a and Example 12–18b are generally considered to be equivalent:

All of the interval progressions presented in this chapter are also valid in their compound forms. For the sake of clarity, however, interval progressions will here be listed only in their simple forms. Compound intervals will only be used for naming progressions when the intervals expand from smaller than an octave to greater than an octave or vice versa.

One voice moves by step, the other by leap:

The second category of contrary-motion interval progressions includes those in which one voice moves by step and the other by leap. One example is a perfect fifth expanding to a perfect octave:

In the first part of this example, the upper voice ascends by step from B to C while the lower voice leaps from E down to C. The same progression in reverse is, of course, also valid.

These roles could also be reversed. In the following example, the upper voice leaps, while the lower voice descends by step:

A third expands to a sixth in the same way, with a step in one voice and a leap in the other:

Both voices move by leap:

Finally, there is the third category of contrary motion in which both voices move by leap. The only permitted progression in this category is the 6–10 (and 10–6) progression:

Notice that the while the soprano moves from B to D, the bass does just the opposite: D to B. This swapping of pitch classes is known as a voice exchange. Voice exchanges are a common technique in music of this style. In analysis, they are often highlighted by using a pair of crossed lines, as shown in Example 12–34.

12.5 Similar motion

A second large category of interval progressions includes those where the two voices move in similar motion. In each of these progressions, one voice moves by step, the other by leap in the same direction. In the following example, we see the two voices forming a third expanding to a fifth, with both moving in the same direction.

Like the second category of contrary-motion progressions, the roles of the two voices may be reversed. In the previous example, the upper voice moved by step while the lower voice moved by leap. In the following example, it is the lower voice that moves by step and the upper by leap:

There are two other such similar-motion interval progressions, 5–6 (and its reverses):

and 6–8 (and its reverses):

There is one special type of similar-motion interval progression which in three- and four-voice settings, occurs mainly between the lowest voice—the bass—and one of the voices sounding above it. In this progression, the upper voice moves by step while the bass leaps by fifth in the same direction:

12.6 Oblique motion

The last type of motion for interval progressions is oblique motion, where one voice remains stationary while the other moves against it by step (or leap). The 5–6 progression is typical:

12.7 Summary

The standard interval progressions presented in this chapter form the backbone of polyphony in tonal Western art music. These progressions are categorized by the type of motion found between the voices: parallel, contrary, and oblique. This list may seem daunting at first and for that reason we have included an overview summarizing them all by category. A complete list may be found in Appendix A. With time and some practice, you will easily become familiar with all of them.