I'd like to be clear about why these additional features are necessary. Taking Documents as an example, we could implement search filters and settings for:

 * Source (except Music doesn't have support for remote sources yet)
 * Content type (Artist, Album, Track)
 * Match (Artist, Album, Track, ...)

In the case of Documents, these types of filters and search settings make sense: you can have a diverse collection of different document types from different sources.

For Music it isn't clear to me why I would need to filter or search in this way. The collection is uniform enough that filters aren't as necessary, and it isn't obvious to me why I would need to search for artist or album, rather than always all fields.

Fixed in https://git.gnome.org/browse/gnome-music/commit/?id=cd9c795832e97fceea6d6714dac5aa392a1d2081