The instrumental category covers works for a single instrument, mostly keyboard and plucked instruments. Keyboard instruments include the piano, harpsichord and organ. The most popular keyboard form is the piano sonata (Haydn, Mozart, Beethoven and Schubert made major contributions). During the Romantic period smaller forms became very popular, among them miniature tone poems and national dances such as mazurkas and polonaises. Many virtuosos/composers also wrote technical display pieces for their own use in concerts, including transcriptions of songs and opera arias. J.S. Bach, Handel, Couperin, Scarlatti and Soler are among the most important composers for the harpsichord. There is also a vast range of music for solo guitar (Sor, Giuliani and many 19th century and contemporary Spanish and Latin American composers) and lute (Weiss, Dowland). The relatively limited number of solo works for other instruments includes music for the solo violin and solo cello. Bach’s sonatas and partitas for violin solo are perhaps the best-known for these.