Open E tuning is a tuning for guitar: low to high, E-B-E-G♯-B-E.[1]
Compared to standard tuning, two strings are two semitones higher and one string is one semitone higher. The intervals are identical to those found in open D tuning. In fact, it is common for players to keep their guitar tuned to open d and place a capo over the second fret. This use of a capo allows for quickly changing between open d and open e without having to manipulate the guitar's tuning pegs.[2]
Open E tuning is often used for slide guitar, as it constitutes an open chord, which can be raised by moving the slide further up the neck. Most notably Duane Allman used open E for the majority of his slide work, such as in "Statesboro Blues".