A concerto (/kənˈtʃɛərtoʊ/; plural concertos, or concerti from the Italian plural) is a musical composition generally composed of three movements, in which, usually, one solo instrument (for instance, a piano, violin, cello or flute) is accompanied by an orchestra or concert band. Its characteristics and definition have changed over time. In the 17th century, sacred works for voices and orchestra were typically called concertos, as reflected by J. S. Bach's usage of the title 'concerto' for many of the works that we know as cantatas. A concerto (/kənˈtʃɛərtoʊ/; plural concertos, or concerti from the Italian plural) is a musical composition generally composed of three movements, in which, usually, one solo instrument (for instance, a piano, violin, cello or flute) is accompanied by an orchestra or concert band. Its characteristics and definition have changed over time. In the 17th century, sacred works for voices and orchestra were typically called concertos, as reflected by J. S. Bach's usage of the title 'concerto' for many of the works that we know as cantatas. The word concerto comes from Italian; its etymology is uncertain, but it seems to originate from the conjunction of two Latin words: conserere (meaning to tie, to join, to weave) and certamen (competition, fight). The idea is that the two parts in a concerto—the soloist and the orchestra or concert band—alternate between episodes of opposition, cooperation, and independence to create a sense of flow. The concerto, as understood in this modern way, arose in the Baroque period, in parallel to the concerto grosso, which contrasted a small group of instruments called a concertino with the rest of the orchestra, called the ripieno. The popularity of the concerto grosso declined after the Baroque period, and the genre was not revived until the 20th century. The solo concerto, however, has remained a vital musical force from its inception to this day. The term 'concerto' was initially used to denote works that involved voices and instruments in which the instruments had independent parts—as opposed to the Renaissance common practice in which instruments that accompanied voices only doubled the voice parts. Examples of this earlier form of concerto include Giovanni Gabrieli's 'In Ecclesiis' or Heinrich Schütz's 'Saul, Saul, was verfolgst du mich'. The concerto began to take its modern shape in the late-Baroque period, beginning with the concerto grosso form developed by Arcangelo Corelli. Corelli's concertino group was two violins, a cello and harpsichord. In J. S. Bach's Fifth Brandenburg Concerto, for example, the concertino is a flute, a violin, and a harpsichord; although the harpsichord is a featured solo instrument, it also sometimes plays with the ripieno, functioning as a continuo keyboard accompaniment. Later, the concerto approached its modern form, in which the concertino usually reduces to a single solo instrument playing with (or against) an orchestra. The main composers of concertos of the baroque were Tommaso Albinoni, Antonio Vivaldi, Georg Philipp Telemann, Johann Sebastian Bach, George Frideric Handel, Pietro Locatelli, Giuseppe Tartini, Francesco Geminiani and Johann Joachim Quantz.The concerto was intended as a composition typical of the Italian style of the time, and all the composers were studying how to compose in the Italian fashion (all'Italiana). The Baroque concerto was mainly for a string instrument (violin, viola, cello, seldom viola d'amore or harp) or a wind instrument (flute, recorder, oboe, bassoon, horn, or trumpet,). Bach also wrote a concerto for two violins and orchestra. During the Baroque period, before the invention of the piano, keyboard concertos were comparatively rare, with the exception of the organ and some harpsichord concertos by Johann Sebastian Bach. As the harpsichord evolved into the fortepiano, and in the end to the modern piano, the increased volume and the richer sound of the new instrument allowed the keyboard instrument to better compete with a full orchestra. Cello concertos have been written since the Baroque era, if not earlier. Among the works from that period, those by Antonio Vivaldi and Giuseppe Tartini are still part of the standard repertoire today. The concertos of the sons of Johann Sebastian Bach, such as C. P. E. Bach, are perhaps the best links between those of the Baroque period and those of the Classical era. It is conventional to state that the first movements of concertos from the Classical period onwards follow the structure of sonata form. Final movements are often in rondo form, as in J.S. Bach's E Major Violin Concerto.