Constructing 4-part texture using triads: Motion

The final installment in our focus on 4-part textures will be how to deal with motion between chords. Whenever you are moving, you have to pick a direction. It is no different with the lines in a voiced chord. Lines within a moving chord have three choices: stay on a common tone (if available), move up or move down. I will break down the types of motion from chord to chord in the common practice order of most desirable to least desirable:

Contrary motion:
This motion is a strongly desired method of moving from chord to chord. When you are moving chords in contrary motion, you are moving the upper voices in the opposite direction of the bass line.

As you can see in this example, the bass voice is moving down while the others voices are moving in the opposite direction. This is a preferred motion between chords during common practice times.

Oblique motion:

Contrary motion and oblique motion are closely related. Think of oblique motion as contrary motion with a common tone if possible.

In this example the tenor and alto voices are moving contrary to the bass, but the soprano line remains on the common tone of G. That is the essence of oblique motion. This motion is also desired in common practice writing.

Similar motion:

Now we are getting to the chord motions that are less desirable because the often lead to spacing or other issues which we will spend a little bit of time on in a future class. In similar motion, the voices are all moving in the same direction as the bass, but avoid moving at the same interval.

You see that all the voices in similar motion are moving in the same direction. The important part of similar motion is that the voices move at different intervals from the bass. The motion in the bass is a 2nd while the motion in the tenor is a 5th, the alto is a 4th, the soprano is a 4th. This motion is not particularly desirable in the common practice but it is generally preferred to...

Parallel motion:

In parallel motion (as in similar motion) the voices move in the same direction as the bass. However, in parallel motion, you have instances where voices move at the same interval of the bass. This is a sound we often embrace in more modern music, but during common practice it was avoided.

In this example all of the voices are moving in the same direction and with the same interval (descending 4th). This sound is the least desirable of all the common practice chord motions. 

**Check out your chord motion in your 4-part texture. Try to identify the type of motion you employ between chords. Where possible see if you can move it up the motion food chain toward contrary or oblique motion. 

You may even notice places where you have elements of different motion combined. Similar motion with a common(oblique) tone or parallel motion combined with contrary motion. In those instances, you want to try to eliminate the less desirable motion while maintaining the more preferred elements.