The modern steel-string acoustic guitar (also known as the flat-top) evolved from the European classical guitar. In the late 1800s, Christian Frederick Martin (founder of C.F. Martin & Co.) developed 'X-bracing'—a internal wooden support system for the guitar's soundboard. This was a revolutionary invention because it allowed the guitar to withstand the immense tension of steel strings, which were becoming popular because they were louder than traditional gut strings. This volume was necessary for the guitar to be heard in larger ensembles and rowdy social settings. The steel-string guitar became the primary instrument for American folk, blues, and country music. Its bright, metallic, and ringing tone is distinct from the soft, mellow sound of a nylon-string classical guitar. The 'Dreadnought' size, also invented by Martin, became the industry standard for its deep bass and loud projection.