Complex sentence: The extremely expensive routing of mechanical key and stop action is unmatched, but consequently is hard to play: the keys must be pressed hard to sound the organ due to all the long, heavy mechanisms that must be moved every time a key is pressed.
Split into simpler sentences: The extremely expensive routing of mechanical sound and stop action is unmatched, but has a relatively uncomfortable playing force. The keys must be pressed hard to sound the organ due to all the long, heavy mechanisms that must be moved every time a key is pressed.