Light opera in the context of "D'Oyly Carte Opera Company"

Musical theatre is a form of theatrical performance that combines songs, spoken dialogue, acting and dance. The story and emotional content of a musical – humor, pathos, love, anger – are communicated through words, music, movement and technical aspects of the entertainment as an integrated whole. Although musical theatre overlaps with other theatrical forms like opera and dance, it may be distinguished by the equal importance given to the music as compared with the dialogue, movement and other elements. Since the early 20th century, musical theatre stage works have generally been called, simply, musicals.

Although music has been a part of dramatic presentations since ancient times, modern Western musical theatre emerged during the 19th century, with many structural elements established by the light opera works of Jacques Offenbach in France, Gilbert and Sullivan in Britain and the works of Harrigan and Hart in America. These were followed by Edwardian musical comedies, which emerged in Britain, and the musical theatre works of American creators like George M. Cohan at the turn of the 20th century. The Princess Theatre musicals (1915–1918) were artistic steps forward beyond the revues and other frothy entertainments of the early 20th century and led to such groundbreaking works as Show Boat (1927), Of Thee I Sing (1931) and Oklahoma! (1943). Some of the best-known musicals through the decades that followed includeMy Fair Lady (1956), The Fantasticks (1960), Hair (1967), A Chorus Line (1975), Les Misérables (1985), The Phantom of the Opera (1986), Rent (1996), Wicked (2003) and Hamilton (2015).

Operetta is a form of theatre and a genre of light opera. It includes spoken dialogue, songs and including dances. It is lighter than opera in terms of its music, orchestral size, and length of the work. Apart from its shorter length, the operetta is usually of a light and amusing character. The subject matter may portray "lovers' spats, mistaken identities, sudden reversals of fortune, and glittering parties". It sometimes also includes satirical commentaries.

"Operetta" is the Italian diminutive of "opera" and was used originally to describe a shorter, perhaps less ambitious work than an opera. Operetta provides an alternative to operatic performances in an accessible form targeting a different audience. Operetta became a recognizable form in the mid-19th century in France, and its popularity led to the development of many national styles of operetta. Distinctive styles emerged across countries including Austria-Hungary, Germany, England, Spain, the Philippines, Mexico, Cuba, and the United States. Through the transfer of operetta among different countries, cultural cosmopolitanism emerged in the previous century. Operetta as a genre lost favor in the 1930s and gave way to modern musical theatre. Important operetta composers include Johann Strauss, Jacques Offenbach, Franz Lehár, and Francisco Alonso.