At that time, the core parts of a score weren't written in advance, so each disciple of a master had to add those parts later (the system was employed in which, when a person wanted to learn certain musical scores it was necessary to enter the school of the master through necessary procedures and become his disciple.)
楽譜の肝心な部分は、弟子が肉筆で加筆するようになっている(師匠に手続きをふんで入門し、門人にならないと、楽譜を教えてもらえない仕組みになっていた）。