The performance would depend on how you interface with the library. I envision a setup where the entire piece is first written using a nice interface, that fron

The performance would depend on how you interface with the library. I envision a setup where the entire piece is first written using a nice interface, that frontend then generates the text file that is passed to Lilypond, Lilypond does its magic (one time!), and then the user has an opportunity to make minor tweaks to the layout or start the cycle anew to fix mistakes.