A steel-string acoustic guitar, is a modern form of guitar descended from the classical guitar, but strung with steel strings for a brighter, louder sound. Strictly speaking, the terms steel-stringed guitar, classical guitar, and folk guitar all refer to acoustic (that is, non-electric) guitars, though some of these terms refer to different types of instruments (nylon-strung vs. steel-strung). The term "acoustic guitar" is a retronym, since before the invention of the electric instrument, all guitars were "acoustic."
The standard tuning for an acoustic guitar is E-A-D-G-B-E (low to high), although many players, particularly fingerpickers, use alternate tunings (scordatura), such as "open G" (D-G-D-G-B-D), "open D tuning" (D-A-D-F -A-D), or "drop D" (D-A-D-G-B-E). A common mnemonic for standard tuning is "Eddie ate dynamite; good-bye Eddie", which aids beginners in remembering the string tuning sequence from low to high.
One variation on the standard acoustic guitar is the 12-string guitar, which sports an additional doubling string for each of the traditional six strings. This guitar was made famous by artists such as Lead Belly, Pete Seeger, and Leo Kottke.
