Cross tuning or cross-tuning (aka scordatura) is an alternative tuning used for the open strings of a string instrument. The term refers to the practice of retuning the strings; it also refers to the various tunings commonly used, or in some contexts it may refer to the AEAE fiddle tuning. In folk music traditions cross-tunings are used to give the instrument a different sound by altering the pitch of string resonances and drones. It may be notated in the normal way, with notes written at the sounding pitch, or the written notes may represent the finger position as if played in regular tuning, while the sounded pitch is altered.
Cross tuning is commonly used on the fiddle in folk music of Appalachia, the southern United States and Scandinavia. The fiddle may be re-tuned in any number of ways in these musical idioms, but there are two common re-tunings. While the standard tuning for open strings of the violin is GDAE—with the G being the tuning of the lowest-pitched string and the E being the tuning for the highest-pitched string—fiddlers playing tunes in the key of D major sometimes employ a tuning of ADAE. In this tuning the open G string is raised to the A directly above it. Even more frequently used is a cross tuning of AEAE for music played in the key of A major. Among fiddlers this is referred to as "cross-tuning." Both of these tunings facilitate a drone on an open string next to the string on which the melody is being played. Relatively well-known American folk tunes that are often played in cross-tuning include "Breaking Up Christmas," "Cluck Old Hen," "Hangman's Reel," "Horse and Buggy," and "Ways of the World."
GDAE is known in some North American Old-Timey fiddling circles as "that Eye-Talian (Italian) tuning," the implication being that it is only one of many possibilities. (On the other hand, in the biography of Arizona fiddler K.C. Kartchner his daughter specifically refers to 'the Italian tuning" as being a cross-tunings which is not GDAE. "Frontier Fiddler - the Life of a Northern Arizona Pioneer" Univ of Arizona Press, 1990). Other tunings include: