Country music started in the hills of the appalachian mountains as bluegrass and gospel before working its way into Nashville and blending with blues. During this time, the guitar found a new tuning called 'high strung' or nashville tuning which is really just standard tuning tuned an octave higher. So, from heavy to light (left to right) each string is still as follows: E, A, D, G, B, E. The difference is that this tuning requires a unique set of strings to accomodate the higher frequency and string tension.
Don't try a standard set of strings for nashville tuning as it could break your guitar! The extreme tension required to tune a string this high requires the following gauge string set: .010 (high E), .014 (B), .009 (G), .012 (D), .018 (A), and .027 (E) although the thin strings from a set for 12 string guitar.
Nashville tuning actually has its roots in African folk music and the sound has a super high 'sheen' to it. Famous american songwriters were quite fond of it as well. Paul Simon would layer a track of nashville tuning on top of his songs to add an almost subliminal high frequency quality. The drawback to this tuning is that it truly requires an extra guitar to leave 'high strung' and chilling in the corner. The guitar often must be adjusted to handle the unique string tension. Smaller guitars are the best choice, since there is little to no bass in nashville tuning. For the adventurous guitarist (or rabid collector), this tuning could be used to add a new dimension to existing tracks or serve as a minimalist texture.
by Ben LongGoogle+