Although the modern twelve-string is derived from the six-string guitar, this twelve-string tuning bears a striking similarity to that of the Baroque guitar, and was possibly even the tuning used on the twelve-string guitars that were built and played as the Baroque guitar evolved to the Romantic and then to the modern Spanish guitar. However these older instruments were probably tuned a little flat of the modern pitch standard, see Baroque guitar.
Used on some electric twelves, particularly for power chord players. Saves breaking octave G strings, which are the only string in the standard tuning tuned above the top E string of a normal guitar. Standard stringing of the Shergold Modulator 12.
Famously used by the Byrds, and also by the Easybeats, Beatles and others, this particular guitar model (still in production) reversed the order of the principal and octave strings.
Early 20th century twelve-strings were just not strong enough for "concert pitch", so were tuned two frets down, and often played with capot 2 to bring them back to "concert". This also meant that the octave G string, now an F, was tuned only one semitone higher than the string designer had intended, not three!
Also known as D tuning.