Overtones vs. Multiphonics?

What’s the difference between an overtone and a multiphonic?

Many people write to me to ask whether multiphonics are the same as overtones. The answer is yes and no! An overtone can be a multiphonic, and a multiphonic can be an overtone, but not all multiphonics are overtones, and neither are all overtones multiphonics. They are two related but separate things.

It makes sense to begin by defining both words. Multiphonic is a little simpler to explain, so we’ll start there. Very simply, a multiphonic is any instance where a wind player (flutist, clarinetist, trombonist, saxaphonist, etc.) produces more than one pitch at a time. These wind instruments aren’t designed to project more than one salient pitch at the same time, so playing a multiphonic is a special thing.

Multiphonics can be (and often are) produced by accident, when the player aims their air ‘just so’ such that two notes are produced simultaneously. This is known as a ‘crack’, and is only one type of many interesting and disastrous mistakes a wind player can make. Good multiphonics don’t sound like cracks though. That ‘just so’ that occurs by accident and causes a crack can be tamed to the point of happening on purpose. With hard work, multiphonics can be tuned the same way a wind player tunes an individual note. They can sound like sonorities, and sometimes harmonies. In fact, chords and chord progressions can be projected, much like a violinist playing double stops.

The difference is that the violinist has more than one string to work with, while the wind player has only a single tube of air. Mastering multiphonics as an art form requires a lot of very specific blowing, including non-traditional shaping of the tongue and the aperture through which you blow.

Enter overtones. Overtones form a specific category of multiphonic. A fingering is blown, and the frequency that normally occurs with that fingering is produced. However, other frequencies, which fall into a specific ratio of twice as high, three-halves as high, four-thirds as high, and five-quarters as high can also be produced if the right combination of angles and speeds are used. These other frequencies, depicted below, are called overtones.

An overtone is a phenomenon of nature. If you pluck a rubber band, it will vibrate in a complex way: The whole rubber band will vibrate, so there will be a force pushing the rubber band at its middle point. But there will be other forces too: the rubber band will have an impetus to vibrate in halves, in thirds, in quarters, and in short, all possible divisions of itself—to infinity! Theoretically, the rubber band divides itself in this way infinitely, and each of these infinite divisions yields a different force upon the rubber band!

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Imagine you are a rubber band molecule, and an infinite number of forces are pushing at you. Where do you end up? In an infinite number of places all at the same time?

Of course, a rubber band is a physical thing; it takes up space in the universe and it doesn’t break into tiny particles when it’s plucked: it stays as a whole, as a rubber band. Its molecules can’t be in an infinite number of places at a single moment, as the forces would have it! So the forces compete with one another, resulting in what is called a sum of motion—each molecule pulling its neighbors along for a ride. The actual molecules of the rubber band move according to the sum of all of the forces. The sum changes over time, as the forces volley with one another, and the result of this changing sum is a series of overtones.

If we were to magically consolidate this series of milli-moments into a single moment of frozen time, every note would sound like the

sound depicted in diagram 1, where each of the overtones sounded equally all at the

same time.

We can’t freeze an evolution into a single moment, so what we actually hear is a

series of versions of diagram 1. The rubber band, and any string of solid matter

(think, piano string, cello string) vibrates in a pattern of overtone frequencies. The

main frequency we hear is called the fundamental. The fundamental is the pitch that

would happen if a string could vibrate purely as a whole, without having the impetus

to divide into parts. The other frequencies that are emitted by the string are called

overtones.

Just as strings produce overtones, so do air tubes. Clarinets, flutes, trumpets all produce overtones, as a

result of the various forces that are placed upon the vibration of the air tube that is

housed and vibrating inside the instrument. In fact, the thing that differentiates a

clarinet from a flute, from a trumpet, from a trombone is the overtone content that is

emitted over time. Clarinets tend to sound purer, because the overtones that are

produced are spaced further apart than on the flute. Trumpets and flutes sound very

similar at the middle of a note, because the overtone content is very similar. However, the beginning of a trumpet note is very different from the beginning of a flute note. Diagram 1 evolves in a very different pattern over time for the trumpet and the flute. Because we don’t hear diagram 1 frozen into a single moment—(instead, we hear the overtone content evolving gradually)—we can recognize whether a sound is from a trumpet or from a flute.

Overtones are present in all flute tones, in varying recipes that can be changed over time by modulating the various angles and speeds at which air streams leave the lips and strike the flute. Skilled artisans take advantage of different overtone recipes to evoke different and changing moods with their tone. A tone that seems hollow and mysterious has very few overtones mixed in, while a tone that is harsh and unsettling has many high overtones. A tone that seems rich and luxurious has a rich mix. Mixing overtones can be thought of like mixing colors on a painter’s palette: by adding a bit of the fifth, we darken our tone; by adding the thirds above that, we brighten the shade and flirt dangerously with stridence; by allowing the fifths and thirds to fade, we sullen the tone. Flutists have a lot of potential for mixing.

Because overtones are produced according to divisions of a string or air-tube, it follows that overtones should all be mathematically related. In fact, this is the case. The first overtone that is produced on a flute (and on a piano or string instrument) is exactly twice the frequency of the fundamental. It’s not a coincidence that the frequency is twice as fast! It’s because this overtone is produced as a result of the forces of motion within the string or air-tube divided into two. As we get higher up the pitches in diagram 1, the pitches get closer and closer together. This is because the string’s/air tube's divisions get smaller and smaller, and smaller and smaller and smaller through infinity.

So, what is the difference between overtones and multiphonics? Well, overtones can be blown so that they sound at the same time as one another. This specific type of multiphonic usually sounds more or less like a major triad, since the first overtones in the overtone series coincidentally produce a major triad. A single air-tube length is being divided into infinite numbers of equal parts, and some of the overtones that emerge are being supported by the various angles and speeds of airstreams that are being projected out of the player’s mouth and against the wall of the flute’s lip plate.

But if overtones were the only way to produce a multiphonic, then the only sonorities we would be capable of producing would be pitches in a single fundamental overtone series! How can we play other sonorities—like minor chords, seventh chords, whole steps and half steps?

The answer is that there is another way of producing a multiphonic, and that is to have two different air tube lengths vibrating at seemingly the same time. This is how we form multiphonics that are not overtones, and this is how we achieve the rich harmonic vocabulary that we have achieved in the world of flute multiphonics.

More on this in another post!

#flute #multiphonics #extendedtechniques #flutephysics #overtones #BonnieMcAlvin #ParallelTransformations #TransformingParellels #FourteenFortnights

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