[Lawrie]

<snip>
I think everything you need can be achieved by different collections. My list in your case would look like this:
Collections inside MobileSheets:
Band1 - Trom1
Band1 - Trom2
Band1 - Tuba
Band2 - Trom1
...
<snip>

Sorry about continuing the hijack...

The problem I see with having MSP manage files is the need to have really, really complex naming conventions.  The way I understand it, every PDF would end up in the same directory so numbers from different bands would also have to have the bands name in the filename - or some other group identifier...

Having been an IT pro (now retired) for more decades than I care to remember, logical management of directory and file structures is ingrained.  I've ALWAYS hated the Apple approach of insulating the user from the file system for this reason.

I haven't finished loading everything yet and I'm already talking 1800 files (individual PDFs)...

My approach works for me - makes management of changes and additions easy via my PC - and to load the database I only need to batch load a particular subdirectory structure, not sort through thousands of files in a single directory.

Of course YMMV.

It's also true I might have misunderstood the MSP file management philosophy, but the repeated warnings about unique filenames makes me confident I have it figured out.