A string is the vibrating element of chordophones such as the guitar, harp, piano (piano wire), and the violin family, that produces sound. Strings are lengths of a flexible material that a musical instrument holds under tension so that they can vibrate freely, but with control. This is to make the string vibrate at the desired pitch, while maintaining a low profile and sufficient flexibility to play in action.
There are two main kinds of strings; plain and wound. "Plain" strings are simply one piece of cylindrical material, commonly consisted of nylon or gut, while "wound" strings have a central core, plus other material which is tightly wound around the string (usually made of various metals).[1]
Prior to World War II, strings of many instruments (including violins and guitars) were composed of a material known as catgut, a type of cord made from refined natural fibers of animal intestines. This was the status quo until the 1950s, when mainstream popularity fell for gut strings, and steel and nylon strings became more favored in string making. Although catgut is still prized by many musicians today, due to its unique sound.[2] The invention of wound strings (particularly steel) was a crucial step in string instrument technology, because a metal-wound string can produce a lower pitch than a plain gut string of similar thickness. This enabled stringed instruments to be made with thinner bass strings.
On string instruments that the player plucks or bows directly (e.g., double bass), this enabled instrument makers to use thinner strings for the lowest-pitched strings, which made the lower-pitch strings easier to play. On stringed instruments in which the player presses a keyboard, causing a mechanism to strike the strings, such as a piano, this enabled piano builders to use shorter, thicker strings to produce the lowest-pitched bass notes, enabling the building of smaller upright pianos designed for small rooms and practice rooms.
Roundwound strings have a bumpy surface profile (the bumps of the winding) that produce friction on the player's fingertips. This causes squeaking sounds when the player's fingers slide over the strings, especially when used on with a guitar amplifier or with an acoustic guitar amplified through a PA system. (Some artists use this sound creatively, such as hardcore punk and heavy metal music electric guitarists who scrape the pick down the lower-pitched strings for an effect.)
electric guitar
Roundwound strings' higher friction surface profile may hasten and fret wear, compared with smoother flatwound strings.
fingerboard
When the core is round, the winding is less secure and may rotate freely around the core, especially if the winding is damaged after use.
Since the 20th century, with the advent of steel and synthetic core strings, most bowed instrument string makers market their strings by tension rather than by diameter. They typically make string sets in three tension levels: heavy, medium, and light (German stark, mittel, and weich). These tension levels are not standardized between manufacturers, and do not correlate to specific diameters. One brand's medium strings may have quite a different tension from another brand's medium. Based on available historical records, gut strings were sold before 1900 in a similar way.
On the other hand, modern gut core strings with metal winding, typically have been sold either ungauged for less expensive brands, or by specific gauge. The Gustav Pirazzi company in Germany introduced the Pirazzi meter (PM) measurement early in the 20th century. One PM equals .05 mm. For example, a 14 1/2 PM gauge string has is .725 mm in diameter. Pirazzi (now known as Pirastro) continues to sell its Oliv, Eudoxa, and Passione brand premium gut core strings by PM gauge. Each string is available in 5 or more discrete gauges. Manufacturers of traditional plain gut strings, often used in historically informed performance, sell their products by light/medium/heavy, by PM, by mm or some combination.
Tuning a stringed instrument such as a guitar to pitch puts the strings under a large amount of strain, which indicates the amount of stress inside the string. Stress is relative to the stretch or elongation of the strings. As the string is tuned to a higher pitch, it gets longer and thinner. The instrument can go out of tune because if it has been stretched past its elastic limit, it will not recover its original tension. On a stress vs. strain curve, there is a linear region where stress and strain are related called Young's modulus. A newer set of strings will often be in a region on the stress vs. strain curve past the Young's modulus called the plastic region. In the plastic region, plastic deformation occurs—deformation the material cannot recover from. Thus, in the plastic region, the relationship is not linear (Young's modulus is no longer a constant). The elastic region is where elastic deformation is occurring, or deformation from where the string can recover. The linear (i.e. elastic) region is where musicians want to play their instrument.[25]
