Guitar String Construction

Depending on the construction of the instrument on which they are used, strings will usually have either a ball or loop at one end to attach the string to the instrument. Strings for some instruments may be wrapped with silk at their ends to protect the string. The color and pattern of the silk can be used to identify the string.

The simplest ones are the Roundwound strings. They have a round core inside and round-winding wire, wound in a tight spiral around it. Such strings are usually simple to manufacture and thus are usually the least expensive. There are several drawbacks, however:

• Roundwound strings have a surface profile (the "bumps" of the winding) that causes "squeaking" sounds when the player's fingers slide over the strings. Whereas some artists use this sound creatively on purpose, this sound is, in general, unwanted.
• Non-flat surface profile also hastens fingerboard and fret wire wear.

The winding is not secured to the core and can rotate freely around it, especially if the winding is damaged after use. It makes it harder to push down and hold the strings with the fingers, and thus impairs the general playing experience.

Flatwound strings also have a round core, but the winding wire has a rounded square cross-section. When tightly wound, such strings have a much shallower profile (in cross-section), thus making them more comfortable to play, less damaging for frets / fretboard and producing quieter squeak sounds from fingers sliding along the string. However, players frequently cite that the sound of flatwound strings differs considerably from the sound of roundwound, with less brightness

Halfwound strings, ground wound strings or pressure wound strings are a cross between roundwound and flatwound, providing both the tonal characteristics of roundwound and the lack of squeaking and the playing feel of flatwound. Such strings are usually made by winding round wire around a round core first, then polishing, grinding (thus the name, ground wound) or pressing the exterior part of the winding until it is practically flat.

Note that polishing process removes almost half of winding wire mass, thus, to compensate for it, manufacturers have to use heavier gauge winding wire. In its turn, thicker winding wire lowers frequency of slide squeaking. Depending on sound processing, it can be a good thing (as squeaking becomes less accented and it will be masked out by performed music) or a bad thing (high-pitched squeaks are much easier to detect and filter out when recording).

Hexwound strings are composed of regular hexagonal core and a tight (usually round) winding that closely fits a hexagonal shape. It solves the second problem: it secures the winding around the core, so it cannot rotate and slip under the fingers. Sometimes it is cited that hexagonal core improves tones due to closer bond between the core and the windingThe drawback is that relatively sharp hexagonal corners are less comfortable for fingers and wear down the fingerboard and fret wire even faster than roundwound strings. Hexwound strings are more commonly used on bass instruments (such as bass guitars).

Source Wikipedia