A theatre director or stage director is a director/instructor in the theatre field who oversees and orchestrates the mounting of a theatre production (a play, an opera, a musical, or a devised piece of work) by unifying various endeavours and aspects of production. The director's function is to ensure the quality and completeness of theatre production and to lead the members of the creative team into realising their artistic vision for it. The director therefore collaborates with a team of creative individuals and other staff, coordinating research, stagecraft, costume design, props, lighting design, acting, set design, stage combat, and sound design for the production. If the production he or she is mounting is a new piece of writing or a (new) translation of a play, the director may also work with the playwright or translator. In contemporary theatre, after the playwright, the director is generally the primary visionary, making decisions on the artistic concept and interpretation of the play and its staging. Different directors occupy different places of authority and responsibility, depending on the structure and philosophy of individual theatre companies. Directors use a wide variety of techniques, philosophies, and levels of collaboration.