Among alternative guitar-tunings, regular tunings have equal musical intervals between the paired notes of their successive open strings. Guitar tunings assign pitches to the open strings of guitars. Tunings can be described by the particular pitches that are denoted by notes in Western music. By convention, the notes are ordered from lowest to highest. The standard tuning defines the string pitches as E, A, D, G, B, and E. Between the open-strings of the standard tuning are three perfect-fourths (E–A, A–D, D–G), then the major third G–B, and the fourth perfect-fourth B–E. In contrast, regular tunings have constant intervals between their successive open-strings:
3 semitones (minor third): Minor-thirds, or Diminished tuning 4 semitones (major third): Major-thirds or Augmented tuning, 5 semitones (perfect fourth): All-fourths tuning, 6 semitones (augmented fourth, tritone, or diminished fifth): Augmented-fourths tuning, 7 semitones (perfect fifth): All-fifths tuning For the regular tunings, chords may be moved diagonally around the fretboard, as well as vertically for the repetitive regular tunings (minor thirds, major thirds, and augmented fourths). Regular tunings thus often appeal to new guitarists and also to jazz-guitarists, as they facilitate key transpositions without requiring a completely new set of fingerings for the new key. On the other hand, some conventional major/minor system chords are easier to play in standard tuning than in regular tuning. Left-handed guitarists may use the chord charts from one class of regular tunings for its left-handed tuning; for example, the chord charts for all-fifths tuning may be used for guitars strung with left-handed all-fourths tuning. The class of regular tunings has been named and described by Professor William Sethares. Sethares's 2001 chapter Regular tunings (in his revised 2010–2011 Alternate tuning guide) is the leading source for this article. This article's descriptions of particular regular-tunings use other sources also.
Standard and alternative guitar-tunings: A review
This summary of standard tuning also introduces the terms for discussing alternative tunings.
Standard
Standard tuning has the following open-string notes:
E2–A2–D3–G3–B3–E4. In standard tuning, the separation of the second (B), and third (G) string is by a major-third interval, which has a width of four semitones.
The irregularity has a price. Chords cannot be shifted around the fretboard in the standard tuning E–A–D–G–B–E, which requires four chord-shapes for the major chords. There are separate chord-forms for chords having their root note on the third, fourth, fifth, and sixth strings.
Alternative
Alternative ("alternate") tuning refers to any open-string note-arrangement other than standard tuning. Such alternative tuning arrangements offer different chord voicing and sonorities. Alternative tunings necessarily change the chord shapes associated with standard tuning, which eases the playing of some, often "non-standard", chords at the cost of increasing the difficulty of some traditionally-voiced chords. As with other scordatura tuning, regular tunings may require re-stringing the guitar with different string gauges. For example, all-fifths tuning has been difficult to implement on conventional guitars, due to the extreme high pitch required from the top string. Even a common approximation to all-fifths tuning, new standard tuning, requires a special set of strings.
Properties
With standard tuning, and with all tunings, chord patterns can be moved twelve frets down, where the notes repeat in a higher octave. For the standard tuning, there is exactly one interval of a third between the second and third strings, and all the other intervals are fourths. Working around the irregular third of standard tuning, guitarists have to memorize chord-patterns for at least three regions: The first four strings tuned in perfect fourths; two or more fourths and the third; and one or more initial fourths, the third, and the last fourth. In contrast, regular tunings have constant intervals between their successive open-strings. In fact, the class of each regular tuning is characterized by its musical interval as shown by the following list:
3 semitones (minor third): Minor-thirds tuning, 4 semitones (major third): Major-thirds tuning, 5 semitones (perfect fourth): All-fourths tuning, 6 semitones (augmented fourth, tritone, or diminished fifth): Augmented-fourths tuning, 7 semitones (perfect fifth): All-fifths tuning The regular tunings whose number of semitones s divides 12 (the number of notes in the octave) repeat their open-string notes (raised one octave) after 12/s strings: For example,
having three semitones in its interval, minor-thirds tuning repeats its open notes after four (12/3) strings; having four semitones in its interval, major-thirds tuning repeats its open notes after three (12/4) strings; having six semitones in its interval, augmented-fourths tuning repeats its notes after two (12/6) strings. Regular tunings have symmetrical scales all along the fretboard. This makes it simpler to translate chords into new keys. For the regular tunings, chords may be moved diagonally around the fretboard. The shifting of chords is especially simple for the regular tunings that repeat their open strings, in which case chords can be moved vertically: Chords can be moved three strings up (or down) in major-thirds tuning, and chords can be moved two strings up (or down) in augmented-fourths tuning. Regular tunings thus appeal to new guitarists and also to jazz-guitarists, whose improvisation is simplified by regular intervals.
Particular conventional chords are more difficult to play On the other hand, particular traditional chords may be more difficult to play in a regular tuning than in standard tuning. It can be difficult to play conventional chords especially in augmented-fourths tuning and all-fifths tuning, in which the wide (tritone and perfect-fifth) intervals require hand stretching. Some chords that are conventional in folk music are difficult to play even in all-fourths and major-thirds tunings, which do not require more hand-stretching than standard tuning. On the other hand, minor-thirds tuning features many barre chords with repeated notes, properties that appeal to beginners.
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