Among alternative tunings for the guitar, all-fourths tuning is a regular tuning.〔:〕 In contrast, the standard tuning has one irregularity—a major third between the third and second strings—while having perfect fourths between the other successive strings. The standard tuning's irregular major-third is replaced by a perfect fourth in all-fourths tuning, which has the open notes
: E-A-D-G-C-F.
Among regular tunings, this all-fourths tuning best approximates the standard tuning.
In all guitar tunings, the higher-octave version of a chord can be found by translating a chord by twelve frets higher along the fretboard. In every regular tuning, for example in all-fourths tuning, chords and intervals can be moved also ''diagonally''. For all-fourths tuning, all twelve major chords (in the first or open positions) are generated by two chords, the open F major chord and the D major chord. The regularity of chord-patterns reduces the number of finger positions that need to be memorized.〔 Jazz musician Stanley Jordan plays guitar in all-fourths tuning; he has stated that all-fourths tuning "simplifies the fingerboard, making it logical".〔
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Among all regular tunings, all-fourths tuning E-A-D-G-C-F is the best approximation of standard tuning, which is more popular. An advantage of standard tuning is that it has many six-string chords, unlike all-fourths tuning.〔 All-fourths tuning is traditionally used for the bass guitar;〔 it is also used for the ''bajo sexto''.〔http://stringedinstrumentdatabase.110mb.com/b.htm〕
==Relation with all-fifths tuning==
(詳細はall-fifths tuning.
All-fourths tuning is based on the perfect fourth (five semitones), and all-fifths tuning is based on the perfect fifth (seven semitones). These perfect-fourth and perfect-fifth intervals are termed "inverse" intervals in music theory, and the chords of all-fourth and all-fifths are paired as inverted chords. Consequently, chord charts for all-fifths tunings may be used for left-handed all-fourths tuning.