FileMaker's Bento may be adequate for your needs (and easier to digest :smileywink:). Try the Bento 30-day free trial.
Verify if Bento's File List field can link to your "Sibelius or Finale engraving file". If it does then Bento should meet your requirements.
There are several Bento templates that might give you some ideas and a starting point (e.g. Digital Media Template).
I have downloaded the trial version of Bento and although I think I can set this up using the Documents Template I can't export the file for others to use (ie does not export mp3 files)
Will FileMaker allow me to export links to files and mp3 files?