Mandolin are used. Usually, courses of 2 adjacent strings are tuned in unison. By far the most common tuning is the same as violin tuning, in scientific pitch notation G–D–A–E, or in Helmholtz pitch notation: g–d′–a′–e″. Note that the numbers of Hz shown above assume a 440 Hz A, standard in most parts of the western world. Some players use an A up to 10 Hz above or below a 440, mainly outside the United States. Other tunings exist, including "cross-tunings", in which the usually doubled string runs are tuned to different pitches. Additionally, guitarists may sometimes tune a mandolin to
String harmonic overtones at the moment when the string is driven. The finger immediately damps all overtones that do not have a node near the location touched. The lowest-pitch overtone dominates the resulting sound. Music using harmonics can contain very high pitch notes difficult or impossible to reach by fretting. Guitar harmonics also produce a different sound quality than fretted notes, and are one of many techniques used to create musical variety. A pinch harmonic (also known as squelch picking, pick harmonic or squealy) is a guitar technique to achieve artificial harmonics in which the player's thumb or index finger on the