Right now this is a style guidline responsible for this kind of thing.

This approach has a few disadvantages:

• not translatable: [unknown], [untitled] will always remain english words
• only plausible for people who know this style guideline
• song titles are indistinguishable from song names that actually start and end with [ and ] like this one

I suggest there should rather be a flag for unknown and untitled.

I made a mockup for the interface which quickly turned out to be naive since a recording can be named after a Song and an unknown Song.