audiences within the performance itself. Interactive theatre – a presentational or theatrical form or work that breaks the "fourth wall" that traditionally separates the performer from the audience both physically and verbally. Musical – a form of theatre combining songs, spoken dialogue, acting, and dance. Off-Broadway – theatrical performances that take place in theatres in Manhattan in New York City with a seating capacity between 100 and 499. Off-Off-Broadway – theatrical productions in New York City that began as part of an anti-commercial and experimental or avant-garde movement of drama and theatre. Off-Off-Broadway theatres are smaller than Broadway and Off-Broadway theatres, and usually have fewer than 100 seats. Off West End – theatrical performances in London that take place in theatres which are not included as West End theatres and usually have seating capacities of around 40 to 400. Opera – an art form in which singers and musicians perform a dramatic work combining text (called a libretto) and musical score, usually in a theatrical setting. Operetta – a genre of light opera, light in terms both of music and subject matter. It is also closely related, in English-language works, to forms of musical theatre. Play – theatrical performance with scripted dialogue between characters. Regional theatre – theatrical performances by a professional or semi-professional theatre company that produces its own seasons. The term regional theatre most often refers to a professional theatre outside New York City. Repertory theatre – Western theatre and opera production in which a resident company presents works from a specified repertoire, usually in alternation or rotation. Revue – multi-act popular theatrical entertainment that combines music, dance and sketches. The revue has its roots in 19th century American popular entertainment and melodrama but grew into a substantial cultural presence of its own during its golden years from 1916 to 1932. Site-specific theatre – any type of theatrical production designed to be performed at a unique, specially adapted location other than a standard theatre. Street theatre – form of theatrical performance and presentation in outdoor public spaces without a specific paying audience. Summer stock theatre – theatres that present stage productions only in the summer. Touring theatre – independent theatre that travels, presented at a different location in each city. Variety show – a combination of acts, especially musical performances and sketch comedy, and normally introduced by a compère (master of ceremonies) or host. Other types of acts