[Frank Cox]

I think you could do that by creating a csv file for each of your pdf files and making it look like this:

title;pages;custom
Stille Nacht;1;Piano

You can automate the creation of the csv files by writing a little script using bash and sed on your Linux computer or if you're using Windows you can probably do something equivalent (though I have no idea how, someone who knows something about Windows scripting would have to help you out there.)

The workflow of the script is:
Read filename to a variable;strip .pdf from the end of the variable; write csv file using the varaiable plus .csv, strip everything up to and including the first dash in the variable, replace space-dash-space with semicolon-1-semicolon; write the variable to the csv file.

Then you just import the csv file instead of the pdf file and that should get you where you want to go.