A string’s gauge is how thick it is. As a general rule, the thicker a string is the warmer its response will be and the more volume it will produce. However, thicker strings are also stiffer. This makes it harder to fret the string and makes it more difficult to execute heavy string bends. Thinner strings are generally brighter and easier to play, but on some instruments they can sound thin and tinny.
Renaissance and Baroque guitars are the ancestors of the modern classical and flamenco guitar. They are substantially smaller, more delicate in construction, and generate less volume. The strings are paired in courses as in a modern 12-string guitar, but they only have four or five courses of strings rather than six single strings normally used now. They were more often used as rhythm instruments in ensembles than as solo instruments, and can often be seen in that role in early music performances. (Gaspar Sanz's Instrucción de Música sobre la Guitarra Española of 1674 contains his whole output for the solo guitar.)[10] Renaissance and Baroque guitars are easily distinguished, because the Renaissance guitar is very plain and the Baroque guitar is very ornate, with ivory or wood inlays all over the neck and body, and a paper-cutout inverted "wedding cake" inside the hole.
All three principal types of resonator guitars were invented by the Slovak-American John Dopyera (1893–1988) for the National and Dobro (Dopyera Brothers) companies. Similar to the flat top guitar in appearance, but with a body that may be made of brass, nickel-silver, or steel as well as wood, the sound of the resonator guitar is produced by one or more aluminum resonator cones mounted in the middle of the top. The physical principle of the guitar is therefore similar to the loudspeaker.

SFCM produces some of the most successful and influential classical guitarists in the world. Spearheaded by renowned faculty and complemented by visiting artists such as Marcin Dylla, the department honors the tradition of the classical guitar while cultivating innovation. The Harris Guitar Collection, housed at SFCM, gives students a chance to see—and play—some of the most extraordinary guitars of the last two centuries.