Harmonic

A harmonic is a special kind of wave that is connected to another wave called the fundamental frequency. In simple terms, if you have a wave that repeats itself regularly—like the swing of a pendulum or the vibration of a guitar string—you can also produce other waves that vibrate at exact multiples of that original speed. These additional waves are called harmonics. For example, if the fundamental frequency is 50 Hz, which is a common speed for electricity to change direction in power lines, the next harmonics might vibrate at 100 Hz, 150 Hz, and so on.

Harmonics are important in many areas, such as music, physics, and communications. In music, musicians use harmonics to create beautiful, high notes and special sounds on instruments like violins and flutes. When a player gently touches a string at just the right spot without pressing it down fully, the string can vibrate in smaller sections, producing a clear, "glassy" tone that is different from the normal notes of the instrument.

In physics and technology, harmonics help explain how different types of waves behave, especially in sound and electrical systems. Understanding harmonics allows scientists and engineers to design better musical instruments, reduce unwanted noise in machines, and improve how we send information through radio waves.

Terminology

In music and sound, harmonics are often called "overtones" or "partials." These words can sometimes be used in the same way, but they have slightly different meanings. A "harmonic" includes all the notes in a special series of sounds, including the main note, called the fundamental frequency. An "overtone" only refers to the notes that are higher than the main note.

Characteristics

Most musical instruments create sounds made of many small, simple tones mixed together. Our ears usually hear these mix of tones as one note, and what makes that note sound unique — like a piano versus a flute — depends on how strong each small tone is.

Instruments like violins or flutes create tones that fit neatly together, matching exact multiples of a main tone, called the fundamental frequency. These are called harmonics. But not all instruments work this way. For example, cymbals and drums create tones that don’t fit this pattern and don’t sound like they have a clear note. Instruments like pianos mix both kinds of tones, which helps them sound rich and full.

Main article: timbre
Main articles: oscillators, human voice
Further information: resonators, transverse flute, trumpets, clarinets, non-linearly, elastic, gut, brass or steel strings, inharmonic partials, pianos, pizzicato, singing bowls, multiphonics, cymbals, Sethares, dynamic tonality, consonance

Partials, overtones, and harmonics

An overtone is any note higher than the lowest note in a combined sound. The strength and frequency of these notes shape the unique sound, or timbre, of a musical instrument. In instruments like strings and winds, these notes are often called harmonics, though technically they are partials.

Many instruments can play higher notes without the main note sounding first. For example, a recorder can play a note an octave higher by a method called overblowing. String instruments can create very clear, high notes called harmonics or flageolets. These are often used to check if strings are in tune. Not all instruments follow this exact pattern, though. Instruments like xylophones and drums can produce notes that don’t fit neatly into a harmonic series.

On stringed instruments

Main article: String harmonic

Harmonics are special notes that can be played on stringed instruments like violins in two ways. First, by moving the bow closer to the bridge of the instrument, you can play a series of harmonics. Second, by gently touching certain points, or nodes, along an open string with your finger, you can produce what are called natural harmonics. These points divide the string into equal parts, such as halves, thirds, or quarters.

When musicians play harmonics, the sound has a delicate, flute-like quality that can add beautiful color to music. While it's rare to play harmonics higher than the fifth note on most string instruments, larger instruments like the double bass can produce even more harmonics because of their longer strings.

Artificial harmonics

Sometimes musicians need to play a special note called an artificial harmonic. This is done by pressing one finger to shorten the string to a certain length, and then using another finger to touch a node for the desired harmonic note.

Other information

Harmonics can be used in music and sound systems. Composer Arnold Dreyblatt plays different harmonics on a special double bass by using a unique bowing technique. Another composer, Lawrence Ball, uses harmonics to create music with electronic tools.