Question

What is the difference between an overtone and a harmonic?

Answer 1

Harmonic versus Overtone.

Explanation:

A harmonic is any of the integral multiplication of the fundamental frequency.
The fundamental frequency `f` is called the first harmonic.
`2f` is known as the second harmonic, and so on.

Let's imagine two identical waves traveling in opposite direction. Let these waves meet each other. The resulting wave obtained by superimposing one onto the other is called Standing wave.
For this system, fundamental frequency `f` is its property. At this frequency the two ends, which are called nodes, do not oscillate. Whereas center of the system oscillates with maximum amplitude and is called antinode.

Figure depicts vibrational modes of an ideal string, producing harmonic `f, 2f, 3f, 4f,` etc. Observe location of nodes and antinodes.

An overtone is defined as any frequency produced by an instrument which is greater than the fundamental frequency. These along with the fundamental are also called partials. Overtones can take any value of the fundamental frequency. 1st overtone is called second harmonic and so on.
Those overtones which are integral multiple of fundamental frequency are harmonics as already explained above.

In a resonant system such as a stringed instrument, plucking of string produces a number of overtones along with the fundamental tone. These give the distinct sound of the instrument. If the instruments produced only the harmonics and no overtones, all instruments will sound exactly the same.

All harmonics are stationary waves. In case of overtones all overtones are not stationary waves. Only those overtones which match the frequencies of the harmonics act as stationary waves.