Watch the Fareed's Trade Secret #12 online guitar lesson by Fareed Haque from Jazz Comping Survival Guide
This is a huge topic. It starts with early classical guitar from the 19th century. Guitars from the 16 and 1700s had doubled strings similar to a 12-string guitar. When guitars went from doubled strings to single strings in the late 1700s, the lovely sound of harmonics became a new timbre available to composers for the guitar. Sors, Giuliani and others used mostly natural harmonics to create illusions of bells in their pieces. Heitor Villa-lobos, one of the great musical geniuses of our time, used harmonics with great innovation. In many ways he is the father of new age guitar. Pretty much everything done by Ralph Towner, Pierre Bansusan, John Abercrombie, Larry Coryell, John McLaughlin on acoustic guitars in the 70s was done 75 years earlier Villa-Lobos.