Bass guitar tuning
Each bass guitar tuning assigns pitches to the strings of an electric bass. Because pitches are associated with notes, bass-guitar tunings assign open notes to open strings. There are several techniques for accurately tuning the strings of an electric bass. Bass method or lesson books or videos introduce one or more tuning techniques, such as: While tuning is mainly done prior to performances, musicians may tune again during a show, typically between songs, either to correct the tuning of the instrument (heat, humidity, string bending, and heavy playing all affect tuning), or to change to a  new tuning, such as dropping the pitch of the E string to D for a song in D major. Amateur musicians tune their own bass, but touring professionals in bands may have a bass tech who tunes their basses. Overview. Most bass guitars have four strings, which are tuned one octave lower than the lowest pitched four strings of an electric guitar E, A, D, G using the equal temperament tuning method and standard pitch. The bass guitar is a transposing instrument, as it is notated in bass clef an octave higher than it sounds, to reduce the need for  ledger lines in music written for the instrument, and simplify reading. Strings and tuning. The standard design for the electric bass guitar has four strings, tuned E, A, D and G, in fourths such that the open highest string, G, is an eleventh (an octave and a fourth) below middle C, making the tuning of all four strings the same as that of the double bass (E–A–D–G). This tuning is also the same as the standard tuning on the lower-pitched four strings on a six-string guitar, only an octave lower. There is a range of  different string types, which are available in many various metals, windings, and finishes. Each combination has specific tonal characteristics, interaction with pickups, and "feel" to the player's hands. Variables include wrap finish (roundwound, flatwound, halfwound, ground wound, and pressure wound), as well as metal strings with different coverings (tapewound or plastic covered). In the 1950s and early 1960s, bassists mostly used flatwound strings with a smooth surface, which have a smooth, damped sound reminiscent of a double bass. In the late 1960s and 1970s, players began using roundwound bass strings, which produce a brighter tone similar to steel guitar  strings, and a brighter timbre (tone) with longer sustain than flatwounds. A variety of tuning options and number of string courses (courses are when strings are put together in groups of two, often at the unison or octave) have been used to extend the range of the instrument, or facilitate different modes of playing, or allow for different playing sounds. Alternative range approaches. Some bassists use unusual tunings to extend the range or get other benefits, such as providing multiple octaves of notes at any given position, or a larger tonal range. Instrument types or tunings used for this purpose  include basses with fewer than four strings one-string bass guitars, two-string bass guitars, three-string bass guitars (session bassist Tony Levin commissioned Music Man to build a three-string version of his favorite Stingray bass) and alternative tunings (e.g., tenor bass). Tuned A–D–G–C, like the top 4 strings of a six-string bass, or simply a standard four-string with the strings each tuned up an additional perfect fourth. Tenor bass is a tuning used by Stanley Clarke, Victor Wooten, and Stu Hamm. Extended-range basses (ERBs) are basses with six to twelve strings—with  the additional strings used for range rather than unison or octave pairs. A seven-string bass (B–E–A–D–G–C–F) was built by luthier Michael Tobias in 1987 for bassist Garry Goodman. Also German bass luthier Warwick built several custom fretless seven-string Thumb NT basses (F#–B–E–A–D–G–C) for Jeroen Paul Thesseling. A piccolo bass resembles a four-stringed electric bass guitar, but usually tuned one full octave higher than a normal bass. The first piccolo bass was constructed by luthier Carl Thompson for Stanley Clarke. To allow for the raised tuning, the  strings are thinner, and the length of the neck (the scale) may be shorter. Several companies manufacture "piccolo" string sets that, with a different nut, can be put on any regular bass.