Open D tuning is an open tuning for the acoustic or electric guitar. The open string notes in this tuning are: D A D F♯ A D. It uses the three notes that form the triad of a D major chord: D, the root note; A, the perfect fifth; and F♯, the major third. The six guitar strings, from lowest pitch to highest, should be tuned as follows: D A D F♯ A D.
When the guitar is strummed without fretting any of the strings a D major chord is sounded. This means that any major chord can be easily created using one finger, fretting all the strings at once (also known as barring); for example, fretting all the strings at the second fret will produce an E major, at the third fret an F major, and so on up the neck.
Open D tuning is very popular with slide guitar (or 'bottleneck') players, as it allows them to play complete chords using the slide. This tuning is also used for regular (non-slide) guitar playing. The full and vibrant sound it produces - particularly on an acoustic guitar - also makes it ideal for fingerstyle playing.
Many new chord shapes and sounds are available with open D tuning. It can offer a strong compositional element that produce markedly different tonal qualities than standard tuning. The full range of major and minor chords, with all their extensions, are available to the player. Many well-known guitarists have used this tuning at some point in their career. For example, Bob Dylan's album Blood on the Tracks was first recorded entirely in Open D tuning. Richie Havens, Joni Mitchell, Bruce Cockburn, Barry Gibb, and Jason Swain have all released recordings featuring this tuning as well. Stone Gossard, from Pearl Jam, uses this tuning when playing the rhythm guitar on "Even Flow", from their Ten album.