Musical theatre is a form of theatre (generally spelled "theater" in the USA, though often spelled "theatre" by people involved in theatre) combining music, songs, dance, and spoken dialogue. It is closely related to opera, frequently being distinguished by the use of popular music of various forms (or at least popular singing styles), the use of unaccompanied dialogue (though some musicals are entirely accompanied, such as Les Misérables, and some operas have spoken dialogue, such as Carmen), often a greater emphasis on dance by the principal performers and chorus, and the avoidance of many operatic conventions (though some operas avoid these, too). Amplification of the singers is usually approved of in larger theatres where musicals are played, while it is generally disapproved of in opera houses.
Introduction
The three main components of a musical are the music, the lyrics, and the book. The book of a musical refers to the spoken (not sung) lines in the play; however, "book" can also refer to the overall dramaticness of a show. The music and lyrics together form the score of the musical; the lyrics and book together are often printed as the libretto (Italian for “little book”). Other components are the direction, choreography, and technical aspects, such as set, costumes, lighting, etc., that generally change from production to production.
Musical theatre works are performed around the world. The big budget Broadway and West End theatre productions in New York City and London have often been creatively matched by Off-Broadway or regional productions, such as The Fantasticks or The Musical, and by the recent development of musical theatre scenes in Germany, Austria, France, Japan, Eastern Europe, and other places.