In animation, a character is coming to life most often by a group effort and through several stages from rough to final clean-up, encapsulating in clean, precise and define series of line drawings.
But line drawing is like hand-writing. So while everyone is aiming to stay on model, by nature, each artist generates drawings that have slight differences in texture that defines a character.
Where in rough pass an appropriate performance is determined, the tie-down stage refines the action, putting character on model and addresses the overall secondary motions such as clothing articles and hairs.
It is easier for animators to control the look of a character but very difficult to be completely in sync with each other over a more exacting feel of something, such as a loose jacket made of certain type of fabric through motion.
To best maintain a consistency to the feel of movement textures, we opted to have one key animator to tie-down the entire sequence. This workflow would unify all scenes in a sequence, appearing seamless while allowing the performance to be contributed by more than one animator.
(Above, scenes animated by (in order of appearance) - Steve Wong, Mike Nguyen, Casey Alexander, Mike Koizumi and tie-down by Mike N.).