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. 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, ground wound, pressure wound 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