A concerto (//; plural concertos, or concerti from the Italian plural) is, from the late Baroque era, mostly understood as an instrumental composition, written for one or more soloists accompanied by an orchestra or other ensemble. The typical three-movement structure, a slow movement (e.g., lento or adagio) preceded and followed by fast movements (e.g. presto or allegro), became a standard from the early 18th century.
The concerto originated as a genre of vocal music in the late 16th century: the instrumental variant appeared around a century later, when Italians such as Giuseppe Torelli started to publish their concertos. A few decades later, Venetian composers, such as Antonio Vivaldi, had written hundreds of violin concertos, while also producing solo concertos for other instruments such as a cello or a woodwind instrument, and concerti grossi for a group of soloists. The first keyboard concertos, such as George Frideric Handel's organ concertos and Johann Sebastian Bach's harpsichord concertos were written around the same time.
In the second half of the 18th century, the piano became the most used keyboard instrument, and composers of the Classical Era such as Joseph Haydn, Wolfgang Amadeus Mozart and Ludwig van 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 Niccolò Paganini, Felix Mendelssohn, Frédéric Chopin, Robert Schumann, Johannes Brahms, Pyotr Ilyich Tchaikovsky and Sergei Rachmaninoff, continued to write solo concertos, and, more exceptionally, concertos for more than one instrument; 19th century concertos for instruments other than the piano, violin and cello remained comparatively rare however. 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. During the 20th century concertos appeared by major composers for orchestral instruments which had been neglected in the 19th century such as the clarinet, viola and French horn.
In the second half of the 20th century and onwards into the 21st a great many composers have continued to write concertos, including Alfred Schnittke, György Ligeti, Dimitri Shostakovich, Philip Glass and James MacMillan among many others. An interesting feature of this period is the proliferation of concerti for less usual instruments, including orchestral ones such as the double bass (by composers like Eduard Tubin or Peter Maxwell Davies) and cor anglais (like those by MacMillan and Aaron Jay Kernis), but also folk instruments (such as Tubin's concerto for Balalaika or the concertos for Harmonica by Villa-Lobos and Malcolm Arnold), and even Deep Purple's Concerto for Group and Orchestra, a concerto for a rock band.
Concertos from previous ages have remained a conspicuous part of the repertoire for concert performances and recordings. Less common has been the previously common practice of the composition of concertos by a performer to performed personally, though the practice has continued via international competitions for instrumentalists such as the Van Cliburn Piano Competition and the Queen Elisabeth Competition, both requiring performances of concertos by the competitors.