I used a semicolon to separate the tags, but the built-in music app in macOS doesn't seem to recognize them as separate tags. As a result, you'll see entries containing only tracks tagged like “Cover; Dance” and “CoverJazz” (not sure why the semicolon was omitted in the latter). At the same time, this track does not appear in “Cover”, “Dance” and “Jazz”.
The same applies to other metadata fields, such as Artist.
How do I get music to work like Foobar2000 or MusicBee, which handle tags as… tags? In these programs, tags have a many-to-many relationship with tracks, where tracks can belong to multiple genres and genres can have multiple tracks.