A repetiteur or “rehearser” is someone who supervises rehearsals for opera and ballet performances, and may also be involved in orchestra rehearsals. Repetiteurs are very skilled in their field, and usually have extensive experience. Some are ex-performers, others are training to become conductors, and others may be pursuing life-long careers as repetiteurs. People who are interested in becoming a repetiteur can spend years working to gain experience so that they can work in this position.
The precise role of the repetiteur varies depending on the production and the company. She or he works closely with the director, conductor, and other members of the artistic staff to develop a vision for the look and feel of the piece and to keep that vision consistent. The repetiteur is familiar with all of the music and all of the parts, and is usually a skilled sight reader of music. Many can also play at least one instrument, such as the piano, for use in rehearsals.
In ballet, the repetiteur teaches the steps, and works with the dancers in rehearsal so that they will work smoothly together. This can include private coaching sessions with individual dancers as well as the larger group. Repetiteurs are very focused on making sure that the steps are done precisely, and that the mood the piece is brought out in the way in which the dancers express themselves.
Operatic repetiteurs help the singers during rehearsal. The repetiteur teaches the singers their parts, and also acts as a vocal coach, going beyond simple teaching to provide advice on bringing out the right pitch, tone, and emotions in the voice. She or he also makes sure that the singers have their parts word perfect, and acts as a prompter in rehearsals as the singers learn their parts. The repetiteur can usually sing along and stand in for singers who are not present, in addition to providing an idea of the score on the piano so that the singers have music to work with.
Especially in the early stages, the performers may work primarily with the repetiteur. As they become more confident in rehearsals, they can start to work with other members of the artistic staff to bring the piece together, until they reach the point where they are rehearsing in costume on a fully set stage. It can take months of rehearsals to get a piece ready for performance when it is new, and even when a production is being remounted, it can take several weeks to get the performers familiar again.