||This article needs additional citations for verification. (June 2011)|
Entr'acte (pronounced: [ɑ̃tʁaktə]), French Entracte, means "between the acts" (German: Zwischenspiel, Italian: Intermezzo, Spanish: Intermedio). It can mean a pause between two parts of a stage production, synonymous to an intermission, but it more often indicates a piece of music performed between acts of a theatrical production. In the case of stage musicals, the entr'acte serves as the overture of act 2 (and sometimes acts 3 and 4, as in Carmen). In films that were meant to be shown with an intermission, there was frequently a specially recorded entr'acte on the soundtrack between the first and second half of the film, although this practice has died out in recent years.
Originally entr'actes resulted from stage curtains being closed for set or costume changes: to fill time as not to halt the dramatic action, to make a transition from the mood of one act to the next, or to prevent the public from becoming restless. In front of the closed curtains, the action could be continued during these entr'actes, albeit involving only players with no scenery other than the curtain, and a minimum of props.
Like an interquel, an entr'acte can take the action from one part of a large-scale drama to the next by completing the missing links. An interquel, however, is a much later innovation. In contrast to an entr'acte, an interquel utilizes the same kind of resources and magnitude as the parts it joins. The Spanish Sainete often performed a similar function.
The role of music 
In traditional theatre, incidental music could also bridge the 'closed curtain' periods: ballet, opera and drama each have a rich tradition of such musical interludes. The literal meaning of the German word, Verwandlungsmusik refers to its original function – "change music". Eventually, entr'actes (or intermezzi) would develop into a separate genre of short theatrical realizations (often with a plot completely independent from the main piece), that could be produced with a minimum of requisites during intermissions of other elaborate theatre pieces. These later entr'actes were distinctly intended to break the action or mood with something different, such as comedy or dance. Such pieces also allowed the chief players of the main piece to have a break. Eventually the idea of being an insert into a greater whole became looser: interlude sometimes has no other connotation than a "short play".
Other dramatic devices 
When the insert was intended only to shift the mood before returning to the main action, without a change of scene being necessary, authors could revert to a "play within a play" technique, or have some accidental guests in a ballroom perform a dance, etc. In this case the insert is a divertimento (the term is Italian; the French divertissement is also used) rather than an entr'acte.
In the French opera tradition of the end of the 17th century and early 18th century (Jean-Philippe Rameau, for example) such divertissements would become compulsory in the form of an inserted ballet passage, a tradition that continued till well in the 19th century. This was eventually parodied by Jacques Offenbach: for example, the cancan ending Orpheus in the Underworld.
By the middle of the 18th century, a divertimento had become a separate genre of light music as well. These divertimenti could be used as interludes in stage works, many of the divertimenti composed in the last half of the 18th century appears to have lost the relation to the theatre, the music in character only having to be a "diversion" in one or another way.
Some more or less elaborate and/or independent entr'actes or intermezzi became famous in their own right, in some cases eclipsing the theatre productions for which they were originally written:
- La serva padrona, a two-act opera buffa by Pergolesi, was intended to break the seriousness of his opera seria Il prigioner superbo (1733). Eventually the intermezzo got more attention than the large-scale work to which it was added (see Querelle des Bouffons).
- Mozart shows his mastery in the finale of the first act of Don Giovanni, where he mixes the divertimento-like dancing (accompanied by a small ensemble on the scene) with the actual singing. The characters mingle, performing light dances, while they're supposed to be chasing each other for murder and rape. The diversion and the drama become a single multi-layered item.
- Bizet's opera Carmen has entr'actes before acts 2, 3 and 4; the one before act 3, featuring flute and harp, is often played in concert performances.
- A comparable 'filmic' interlude was foreseen in the early 1930s by Alban Berg for his opera Lulu, between the two scenes of the central act. In this case Berg only composed the music and gave a short schematic scenario for a film, that was not yet realised when he died in 1935. The Lulu interlude film, in contrast to the previous example, was intended to chain the action between the first and second half of the opera. Because of the completely symmetrical structure of this opera, the filmic interlude of Lulu is, in a manner of speaking, the axis of the opera.
- Interludes of the divertimento kind can be found in Leoš Janáček's last, sombre opera From the House of the Dead (1928): releasing the tension after Skuratov's disheartening tale at the centre of the second act, two an "opera" and a "pantomime" within the larger opera are executed consecutively by a cast of prisoners, both presentations farcical variations on the Don Juan theme, and mirroring the religious ceremony divertimento before the Skuratov tale.
- Also, the first publicly performed furniture music composed by Erik Satie was premiered as entr'acte music (1920 – the play for which it was written fell into oblivion), with this variation that it was intended as background music to the sounds the public would usually produce at intermission, walking around and talking. Allegedly, the public did not obey Satie's intention: they kept silently in their places and listened, trained by a habit of incidental music, much to the frustration of the avant-garde musicians, who tried to save their idea by inciting the public to get up, talk, and walk around.
- Most of the film adaptations of Broadway musicals shown in roadshow format feature entr'actes during the intermission, which make use of music from the production.
- Fisher, Stephen C (1992), 'Interlude' in The New Grove Dictionary of Opera, ed. Stanley Sadie (London) ISBN 0-333-73432-7
The dictionary definition of entr'acte at Wiktionary