Open C tuning

When the guitar is strummed without fretting any strings, a C-major chord is sounded.

[2] 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".

[9] 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 which enables one-finger minor chords.

Like other cross-note tunings, it also allows major chords to be fretted with one adjacent finger.

The open-C overtones tuning has the same range as NST, which can use extreme strings (.011 and .059 inches).