Plucked stringed instrument. It normally has six strings, a fretted fingerboard, and a soundbox with a pronounced waist. It probably originated in Spain in the early 16th century. By 1800 it was being strung with six single strings; 19th-century innovations gave it its modern form. Modern classical guitar technique owes much to Francisco Tárrega (1852–1909), and Andrés Segovia gave the instrument prominence in the concert hall. However, it has always been primarily an amateur's instrument, and it remains an important folk instrument in many countries. The 12-string guitar is strung in six double courses. The Hawaiian, or steel, guitar is held horizontally and the strings are stopped by the pressure of a metal bar, producing a sweet glissando tone. The electric guitar represented a major development. Electric pickups were attached to the acoustic guitar in the 1920s. In the 1940s Les Paul invented the solid-body guitar; lacking a soundbox, it transmits only the string vibrations. With its long-sustained notes, affinity for strong amplification, and capacity for producing wailing melodic lines as well as harshly percussive rhythms, it soon became the principal instrument of Western popular music.