How have guitars changed over the years?
Since the six-string guitar emerged at the beginning of the 19th century, they have gotten larger. People started putting metal strings on them in the late 19th and early 20th centuries. Of course their shapes have changed a lot. Arch top guitars were very popular for awhile. They seem to have died out quite a bit. Arch top has a top and back more like a cello than the standard flat top guitar that we normally play today. Guitars have acquired, of course, electric pickups. Some have midi interfaces so you can play them with synthesizers. There are a variety of different pickup systems for acoustic electrics. Numbers of strings have changed some. There have been movements toward the seven-string guitar, and the ten-string guitar. There have also been five-string guitars, four-string guitars, twelve-string guitars. There are many styles and designs of guitar, and new ones are being tried and many discarded as time goes by.