[BRX]

I do plan on adding a "fix path" type utility to the Windows 10 version, but it will be limited to folders under the storage location, as that is all the app is granted access to. 

That should be sufficient in general. But then the audio files can't be in a separate folder outside of the storage location. Or is it possible to set the whole partition (D:/) as storage location and still have explicitly D:/sheets and D:/audio as the directories MSP uses and needs access to?

The filter would only apply to what exists on the server device, so that would cause other songs on the client device that might not exist on the server to be ignored. Is that basically what you want? 

Yes, I think that's completely sufficient. I do think this feature will mostly be used to supply the data from a "master" to "slaves". (And it doesn't make much sense to sync setlists both ways anyway) And if indeed a merge of a collection or album is needed, then you could simply reverse the roles of server and client for a second sync, right? Don't make this messier than I wanted. :-)