In the second half of the 18th century, the piano became the most used keyboard instrument, and composers of the Classical Era such as Haydn, Mozart and Beethoven each wrote several piano concertos, and, to a lesser extent, violin concertos, and concertos for other instruments. In the Romantic Era, many composers, including Paganini, Mendelssohn, Chopin, Schumann, Brahms, Tchaikovsky and Rachmaninoff, continued to write solo concertos, and, more exceptionally, concertos for more than one instrument. In the first half of the 20th century, concertos were written by, among others, Maurice Ravel, Edward Elgar, Richard Strauss, Sergei Prokofiev, George Gershwin, Heitor Villa-Lobos, Joaquín Rodrigo and Béla Bartók, the latter also composing a concerto for orchestra, that is without soloist.