The concerto grosso is one of the most important instrumental forms in the Baroque period. It was based on the idea of "competing in friendly rivalry" between a small group of instruments and the whole orchestra.
Some of the most famous concerti grossi include Bach's "Six Brandenburg Concertos", and more than 450 concertos by Vivaldi.
Vivaldi's concertos display his preference for a three-movement-cycle. The outer movements are usually written in the "Ritornello" form, in which a number of elements are quoted again in whole or in part, while the connecting "Episodes" (dominated by the soloists) usually lead to new keys and introduce new thematic material.
Most of the slow movements are in a binary form and resemble the pathetic type of arias. The latter require fine musicianship, technique, and a wonderful voice. The small group of soloists is usually called "Concertino" or "Principale", while the whole orchestra is called "Tutti", "Concerto", or "Ripieni".
