Overtone Series, Introduction

There are several reasons why pitches work well together in melodies and chords. In this writing, I will address only one reason: the acoustical properties of sound.

The acoustical properties of pitch show us that any one pitch is made up of many vibrations, different wave-lengths that we hear as one sound. The vibrations of a sound move so quickly that we hear (usually) only one final sound, the resulting pitch. For example, the pitch we call “middle C” is a sound that vibrates at 256 vibrations per second.

If we dissect the composite 256 vibrations, we’d find others of different frequencies that would actually create different pitches – other vibrations that would create a pitch other than “middle C.” These other vibrations are called overtones. Think of them as secondary vibrations. Overtones are also called harmonics and multiples. A pitch’s overtones play an important role in defining the pitch’s sound.

Overtones not only help form each pitch, they contribute to the tension and ease formed by the relationship of one pitch to another. The relationship of pitch to pitch linearly and vertically and the relationship of chord to chord – even contributing to rock music’s power chord progressions!

Pitches and chords, because of the overtone series of each pitch, almost function like verbs, nouns, and adverbs serving one another in a sentence.

How does the overtone series work? Every pitch has its own overtone series. The pitch in question is called the fundamental. It’s the fundament that will generate an overtone series (although, in reality, you only hear the fundamental, usually). The sound you hear as middle C is a composite of its overtone series. So, what are the other vibrations, the overtones found in middle C? The first overtone is the octave. A kind of reinforcement of middle C itself, except higher. The vibrations are doubled, instead of 256 vbs (vibrations per second) it’s 512. The next prominent overtone found in middle C would form the pitch “G” if we extracted it from its fundamental. “G,” a fifth higher than middle C (count up 5 starting from “C” . . . c,d,e,f,g). The next prominent overtone generated by “C” is the pitch “E.” Already, the overtones mentioned form a triad, C, E, G – the pitches that create a C major triad.

To summarize, any single pitch generates overtones. The most prominent overtones generated by “C” are used to create the C major triad (C,E,G). That’s no accident. Early writers of music, theoretically could have used most any notes together and called them chords. But they used the same notes generated by a fundamental. It’s an organic notion very much in tune with that times thinking about universal order!