[smw]

On the pc I already had several databases that contain song information, including metadata. So I wrote a tool that extracts the metadata from the databases and stores it directly into the MSPro database. This works fine for me, I can quickly add all the relevant metadata (song title, artist, composer, key, tempo, signature, capo, ...) to the MSPro songs. It is, howver, pretty much hard wired for my situation.

That sounds great.  It wouldn't work for me, though, simply because I don't have my metadata in a database to begin with; my organization on the Linux side is strictly based on the directory structure where the files are stored.

I can imagine that it would be possible to supply externally generated metadata information about songs to MSPro, for example in the form of a JSON data file.

I admit I wouldn't have thought of that, but for my own use the old style batch import is still the best fit -- although the modification proposed here would be even better.