The Physics of Everyday Stuff - The Guitar
If you pluck one of the string on a guitar or bass, you are doing something . frequency of Hz: see this link for a table), then the harmonics would have the . As a result, the 1st overtone on a string is slightly sharper than an octave, the next. In the course of studying the overtones, or harmonics of a string fixed at both called standing waves, and they satisfy the relationship between wavelength and . Guitar Harmonics Lesson - A lesson covering the various types of harmonics that can be played on a guitar and how to play them.
The figure shows the musical notation for the first twelve harmonics on a C string. When you play the sound file, listen carefully to the pitch. The seventh and eleventh harmonics fall about halfway between notes on the equal tempered scale, and so have been notated with half sharps.The Physics of Harmonics
You can produce these pitches on a stretched string: Touching the string produces a node where you touch, and so you excite mainly the mode which has a node there. You will find that you can play bugle tunes using harmonics two to six of a string.
OVERTONES HARMONIC AND INHARMONIC
The twelfth fret, which is used to produce the octave, is less than half way along the length of the string, and so the position where you touch the string to produce the 2nd harmonic — halfway along the string — is not directly above the octave fret. I said "idealised" string above, meaning a string that is completely flexible and so can bend easily at either end.
In practice, strings have a finite bending stiffness and so their effective length the "L" that should be used in the above formulae is a little less than their physical length. This is one of the reasons why larger strings usually have a winding over a thin core, why the bridge is usually at an angle that gives the fatter strings longer lengths and why the solid G string on a classical guitar has poor tuning on the higher frets.
What's the difference between overtones and harmonics? - Music: Practice & Theory Stack Exchange
There is also an effect due to the extra stretching of a string when it is pushed down to the fingerboard, an effect which is considerable on steel strings. An exercise for guitarists.
So the various modes and thus the overtones of the string are approximately harmonics but not perfectly so. An interesting other case are free reeds like in a harmonica or accordion.
The reed travels through a reed plate with slots, a metal reed basically a rectangular strip of metal blocking the slot is mounted on one side and sort of punches hard holes into the air stream when bending back and forth through the slot.
Since the punching-holes-in-the-air-stream act is periodic, the resulting overtone-rich sound does not have any disharmonicity.
String harmonic - Wikipedia
However, the reed action itself has higher modes: Now free reeds are not just flat but are profiled in a manner where bending the reeds stronger will still result in the same frequency accordion or will result in bent pitches harmonica. Because of that profile, the metal overtones are usually so far away from the harmonics that they don't get excited. However, when tuning such reeds, one scratches or files the reed in different places depending on whether it needs to go up or down in pitch.
In the process of tuning it may happen that one of the vibrating modes comes close to an actual harmonic.
- Difference Between Harmonics and Overtones
In that case, it will get excited and interfere with the air harmonics from the "punching a hole in the airstream" act. The reed will sound unclean, and it will suffer quite more mechanical stress due to the additional mode it vibrates with in almost-resonance.
Tuning the reed off and then back again might get rid of the problem. So with free reeds actually, the non-free ones as wellyou don't want any overtones in the reed action itself.