Complex sentence: Most organs are operated by cardboard'books' or paper rolls, these are read through a'keyframe' or'tracker bar' using rollers operated by a motor or wheels and a belt connected to the main drive.
Split into simpler sentences: Most organs are operated by cardboard'books' or paper rolls. These are read through a'keyframe' or'tracker bar' using rollers operated by a motor or wheels and a belt connected to the main drive.