Open C tuning

Open C tuning is an open tuning for guitar. The open-string notes form a C major chord, which is the triad (C,E,G) having the root note C, the major third (C,E), and the perfect fifth (C,G). When the guitar is strummed without fretting any strings, a C-major chord is sounded. By barring all of the strings for one fret (from one to eleven), one finger suffices to fret the other eleven major-chords.

An open C tuning

Examples

There are several open C tunings.

Repetitive C-E-G-C-E-G

The English guitar uses a repetitive open-C tuning

C-E-G-C-E-G,

which is approximately a major-thirds tuning,^[1] specifically

C-E-G♯-C-E-G♯=C-E-A♭-C-E-A♭.

"C5" variant C-G-C-G-G-E

This open C tuning was used by Soundgarden for songs including Pretty Noose, Burden in My Hand, and Head Down. Chord sequences often omit the high E string, leaving the power chord ubiquitous to Grunge music.^[2]

C-G-C-G-C-E

C-G-C-G-C-E.^[3]

This open C tuning was used by William Ackerman for his "Townshend Shuffle", by John Fahey for his tribute to Mississippi John Hurt,^[4] and by Led Zeppelin's Jimmy Page for "Friends".^[5][6] It is also used by Devin Townsend for the vast majority of his work (The Devin Townsend Project, Strapping Young Lad, Casualties of Cool).^[7]

Overtones C-C-G-C-E-G

C-C-G-C-E-G^[8]

Another open C tuning uses the harmonic sequence (overtones) of the note C. When an open-note C-string is struck, its harmonic sequence begins with the notes (C,C,G,C,E,G,B♭,C). The root note is associated with a sequence of intervals, beginning with the unison interval (C,C), the octave interval (C,C), the perfect fifth (C,G), the perfect fourth (G,C), the major third (C,E), and the minor third (E,G); in particular, this sequence of intervals contains the thirds of the C-major chord {(C,E),(E,G)}.^[9]

C-minor open chord: Cross-note tuning

Flattening this open tuning's open-note E to E♭ changes the open chord from C-major to C-minor, so producing the cross-note tuning

C-C--G-C-E♭-G

which enables one-finger minor chords. Like other cross-note tunings, it also allows major chords to be fretted with one adjacent finger.^[10]

Relation to new standard tuning

Many of the notes from the harmonic sequence for C appear in the new standard tuning (NST),^[11] which is a nearly regular tuning based on perfect fifths; NST also has (D,A) from the pentatonic scale on C:

C-G-D-A-E-G

NST is used in Guitar Craft (a school of guitar playing founded by King Crimson's Robert Fripp). The open-C overtones tuning has the same range as NST, which can use extreme strings (.011 and .059 inches).^[12]

C-C-G-C-E-C

C-C-G-C-E-C

Using a high C rather than the high G of the overtone series, this open C tuning was used by Mick Ralphs for the songs "Can't Get Enough" and "Movin' On" on Bad Company's debut album. Ralphs said, "It needs the open C to have that ring," and "it never really sounds right in standard tuning".^[13]