Devised theatre – frequently called collective creation – is a method of theatre-making in which the script or (if it is a predominantly physical work) performance score originates from collaborative, often improvisatory work by a performing ensemble. The ensemble is typically made up of actors, but other categories of theatre practitioners may also be central to this process of generative collaboration, such as visual artists, composers, and choreographers; indeed, in many instances, the contributions of collaborating artists may transcend professional specialization. This process is similar to that of commedia dell'arte and street theatre. It also shares some common principles with improvisational theatre; however, in devising, improvisation is typically confined to the creation process: by the time a devised piece is presented to the public, it usually has a fixed, or partly fixed form. Historically, devised theatre is also strongly aligned with physical theatre, due at least in part to the fact that training in such physical performance forms as commedia, mime, and clown tends to produce an actor-creator with much to contribute to the creation of original work.