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
Banjo often with a higher string action. The modern five-string banjo is a variation on Sweeney's original design. The fifth string is usually the same gauge as the first, but starts from the fifth fret, three-quarters the length of the other strings. This lets the string be tuned to a higher open pitch than possible for the full-length strings. Because of the short fifth string, the five-string banjo uses a reentrant tuning—the string pitches do not proceed lowest to highest across the fingerboard. Instead, the fourth string is lowest, then third, second, first, and the fifth string is highest. The short