Chords--What Are They?

Here’s an intriguing mystery. Why is it that, when you add one note to a pair of different notes, you get a sound that is two or three times fuller. The sound is not enhanced by the bare 50%. It sounds much bigger, fuller, more complete.

Is it just a cultural factor of Western harmony? Or is there a scientific explanation in terms of overtones, cross vibrations and harmonic perception?

I believe both factors are important and lean towards the scientific opinion that the output of three harmonically related tones exceeds the input.

Chords are apparently a modern discovery. Up until the Renaissance the musical standard was melody embellished only by a bass line. This tradition persisted in Irish harpers right up until Carolan, and perhaps even to the end of the 18th century.

Unlike the harpers who preceded Carolan, his compositions were written in music notation. Unfortunately, only the melody was written, the bass line was included. We can only guess at how he played his tunes with the bass line added.

Nowadays, Carolan's tunes are played with full chordal accompaniment, just like any popular song or tune.

How is it this kind of music sounds so natural and logical to us? How did it come to rule over the previous music?

The Boom Chuck World

We know the sound. We’ve heard it all our lives. Boom-chuck, boom-chuck. Boom is the bass note, chuck is the chord. So, what’s really happening in boom-chuck land?

As we go into the theory of chords, let’s pause to fill out the history between today's music and music of a melody with bass notes added. (This pairing of notes likely had an occasional in-between note added. Just a guess.) The purposeful addition of third and fourth voices during the Renaissance transformed music.

First there were chords occurring as independent voices moved and created them while changing according to certain rules that seemingly created pleasant sounds. It’s called counterpoint. Each voice is on its own. To make chords and voice leading create dynamic chord progressions was very intricate. Palestrina, in the 16th century, is considered to have pushed this concept to its highest form.

Somehow out of this rich mix of four independent voices, chords were heard as having their own validity. Suddenly there was a single melody line with chordal accompaniment.
The underlying reality of physics explains the emergence of chords as inevitable at some point. There is an expression of sound in the triad that is completely in harmony with the natural world. To understand the physics behind chords we must look at the overtone phenomenon.

This is where most music theory texts begin. That makes sense from the academic, theoretical point of view. The hard part is when you know nothing about the practical aspects of music theory. Then, all the verbiage about overtones just seems irrelevant.

If you have been following my YouTube series about music theory up to the discussion of chords, you are ready for an “Ahah!” moment.

The Physics of Chords

When a vibrating string, or column of air in a tube, or a tuning fork emits a musical note, it also makes other notes as a natural consequence. The fundamental note is made by the whole length of the vibrating string, column of air or metal bar. There are other vibrations that are different and secondary.

For example, there is a secondary vibration that occurs from the midpoint of the string, etc. to the ends. The midpoint is called a node in physics. That secondary vibration creates a pitch an octave higher than the fundamental tone. The speed of the vibration from the node to the end is twice as fast as the speed of the whole vibrating object.

Pythagorus gets credit for having discovered the physics of vibrating strings. He found that the secondary tones were produced by division of the whole string by whole numbers. In other words, nodes occur naturally at the halfway mark, at the one third marks, at one fourth, one fifth, and so on.

The tones produced by these nodal divisions are called overtones. The first one, as said before, is an octave higher. When the string is divided into three parts, the overtone is a fifth higher than the octave. Then the one fourth creates the second octave. Finally, for our purpose, the division into fifths brings out the third above the second octave.

When we reduce these tones by eliminating the octave leaps, we get these three notes: one, five and three, the basic triad built upon the fundamental tone.
Thus, physics shows that the triad is a natural property of the vibrating object that produces a definite pitch or musical tone.

Why did it take so long for musical culture to evolve the melody with chord accompaniment from just melody and bass? I don’t have an answer for that question. The music of the east, including India, China and Japan did not develop this pattern until influenced by the West. The history of music tells the what, and something of the how, but not the why.

August 2008