Inbetweening is not merely putting line in between line but actually moving shapes and volumes to conform to some predetermined action. True, when inbetweening a slow movement where the volumes are very close together, one sees only line going between line
but when inbetweening a broader movement the lines will be further apart and the volume itself must be considered or
in the first case, inbetweening is usually pretty mechanical, i.e., put one line in between two others and that’s it. In the broader movement the lines may be ...