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
Violin comparable to that of fine full size violins. 5 String violin sizes may differ from the normal 4 string. The instrument which corresponds to the violin in the violin octet is the mezzo violin, tuned the same as a violin but with a slightly longer body. The strings of the mezzo violin are the same length as those of the standard violin. Violins are tuned by turning the pegs in the pegbox under the scroll, or by adjusting the "fine tuner" screws at the tailpiece. All violins have pegs; fine tuners (also called "fine adjusters") are optional. Most fine tuners