All rooms in a recording studio may have a reconfigurable combination of reflective and non-reflective surfaces, to control the amount of reverberation. In animation, vocal performances are normally recorded in individual sessions, and the actors have to imagine (with the help of the director or a reader) they are involved in dialogue (as opposed to a monologue). Animated films often evolve rapidly during both development and production, so keeping vocal tracks from bleeding into each other is essential to preserving the ability to fine-tune lines up to the last minute. Sometimes, if the rapport between the lead actors is strong enough and the animation studio can afford it, the producers may use a recording studio configured with multiple isolation booths in which the actors can see each another and the director. This enables the actors to react to one another in real time as if they were on a regular stage or film set.