In music, an intermezzo (pl. intermezzi), in the most general sense, is a composition which fits between other musical or dramatic entities, such as acts of a play or movements of a larger musical work. In music history the term has had several different usages, which fit into two general categories: the opera intermezzo and the instrumental intermezzo.
In some cases the intermezzo repertory spread more quickly than did the opera seria itself; the singers were often renowned, the comic effects were popular, and intermezzi were relatively easy to produce and stage. In the 1730s the style spread around Europe, and some cities--for example Moscow--recorded visits and performances by troupes performing intermezzi years before any actual opera seria were done.
In the 19th century the intermezzo acquired another meaning: an instrumental piece which was either a movement between two others in a larger work, or a character piece which could stand on its own. These intermezzi show a wide variation in the style and function: in Mendelssohn's incidental music to A Midsummer Night's Dream the intermezzo serves as musical connecting material for action in Shakespeare's play; in chamber music by Mendelssohn and Brahms, the intermezzi are names for interior movements which would otherwise be called scherzi; and the piano intermezzi by Brahms, some of his last compositions, are sets of independent character pieces not intended to connect anything else together. Stylistically, intermezzi of the 19th century are usually lyrical and melodic, especially compared to the movements on either side, when they occur in larger works. The Brahms piano intermezzi in particular have an extremely wide emotional range, and are often considered to be some of the finest character pieces written in the 19th century.
Opera composers sometimes wrote instrumental intermezzi as connecting pieces between acts of operas. In this sense an intermezzo is similar to the entr'acte. The most famous of this type of intermezzo is probably the intermezzo from Cavalleria Rusticana, by Pietro Mascagni. Puccini also wrote intermezzi for Manon Lescaut and Madama Butterfly, and examples exist by Wolf-Ferrari, Delius and others.
In the 20th century the term was used occasionally. Shostakovich named one movement of his dark String Quartet No. 15 "intermezzo"; Bartók used the term for the fourth movement (of five) of his Concerto for Orchestra.