In contrast to the five double-strings of the Baroque period, the guitar of the Classical and Romantic periods had six single-strings. Antonio de Torres, “the most important Spanish guitar maker of the 19th century,” created the forerunner of the modern classical guitar.
Though scholars have overlooked its status in classical music, from the late 18th to the early 19th century the guitar attained significant popularity. Fernando Sor, Mateo Carcassi, and Mauro Giuliani were among the most well-known of the guitarist-composers. Famous composers such as Franz Schubert, Hector Berlioz, and Niccolo Paganini also wrote music for the guitar.
The first guitar constructed with single strings rather than pairs of strings was built in 1774 by Ferdinando Gagliano in Naples, Italy. This guitar had 5 single strings, brass frets, and a figure-8 shaped tuning head.
The first six-string guitar was built in 1779 by Gaetano Vinaccia, again in Naples, Italy. France and Spain also began to create guitars with six single strings. The guitar was also increasingly given more definite curves and a larger body. Instead of tied gut, frets were made with fixed bits of harder material, eventually with metal. Wooden keys were later substituted with metal tuning keys.