There are various kinds of mandolins in use in Italy; they bear the names of cities or regions such as the "Roman", the "Lombard", the "Genovese", and the "Neapolitan" mandolin. (see also: mandolin). They may differ in size, shape, number of strings and tuning. The traditional Neapolitan mandolin is tear-shaped with a bowl back and a uniquely cut and shaped front (sounding board); it has eight strings paired into the four violin tunings of g, d', a', and e'. The strings are played with a plectrum, producing the rapid and characteristic tremolo sound as the plectrum moves rapidly over unison strings. In that configuration, the Neapolitan mandolin started to be manufactured widely in Naples in the mid-18th century.