Other attributes
A string is the vibrating element that produces sound in string instruments such as the guitar, harp, piano (piano wire), and members of the violin family. Strings are lengths of a flexible material that a musical instrument holds under tension so that they can vibrate freely, but controllably. Strings may be "plain", consisting only of a single material, like steel, nylon, or gut, or wound, having a "core" of one material and an overwinding of another. This is to make the string vibrate at the desired pitch, while maintaining a low profile and sufficient flexibility for playability.
The invention of wound strings, such as nylon covered in wound metal, was a crucial step in string instrument technology, because a metal-wound string can produce a lower pitch than a catgut string of similar thickness. This enabled stringed instruments to be made with less thick 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.
There are several varieties of wound strings available.
The simplest wound strings are roundwound—with round wire wrapped in a tight spiral around either a round or hexagonal core. Such strings are usually simple to manufacture and the least expensive. They have several drawbacks, however:
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 electric guitar 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.)
Roundwound strings' higher friction surface profile may hasten fingerboard and fret wear, compared with smoother flatwound strings.
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.
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Flatwound
Flatwound strings also have either a round or hex core. However, the winding wire has a rounded square cross-section that has a shallower profile (in cross-section) when tightly wound. This makes for more comfortable playing, and decreased wear for frets and fretboards (this makes them a popular choice for fretless instruments). Squeaking sounds due to fingers sliding along the strings are also decreased significantly. Flatwound strings also have a longer playable life because of smaller grooves for dirt and oil to build up in.
On the other hand, flatwound strings sound less bright than roundwounds and tend to be harder to bend. Flatwounds also usually cost more than roundwounds because of less demand, less production, and higher overhead costs. Manufacturing is also more difficult, as precise alignment of the flat sides of the winding must be maintained (some rotation of the winding on roundwound strings is acceptable).
Modern bowed strings are plain (typically the higher-pitched, thinner strings) or flatwound, to allow smooth playing and reduce bow hair breakage. There is a niche market for roundwound fiddle strings.
Halfwound strings, ground wound strings, or pressure wound strings are a cross between roundwound and flatwound. Such strings are usually made by winding round wire around a round or hex core first, then polishing, grinding (thus the name, ground wound) or pressing the exterior part of the winding until it is practically flat. This results in the flat, comfortable playing feel of flatwounds, along with less squeaking, with a brightness generally between roundwounds and flatwounds. The polishing process removes almost half of the winding wire's mass; thus, to compensate for it, manufacturers use winding wire of a heavier gauge. Because of the extra manufacturing process involved, they are normally more expensive than roundwounds, but less than flatwounds.
There are two types, or shapes, of core wire typically used in wound strings.
Hexcore strings are composed of hexagonal core wire and a tight (usually round) winding. Hexcore string design prevents the winding from slipping around the core – which can occur with round core strings. This may improve tuning stability, flexibility, and reduce string breakage, compared to round core strings.
Round core strings are composed of regular round core and a tight (usually round) winding. Round core is the traditional "vintage" way of manufacturing and results in a greater contact between the winding and the core of the string.
