Searching for "Standalone Recording"

Any hint how to do this with the Search on MusicBrainz ?

Search “Recording” in the quick search box top right of the page, or use the Search menu top centre of the page where more details can be added to the search.

What I mean is especially the STANDALONE recording type which is not part of a release

Search for recordings without release title (-release:*) but it is known to not return all of them: SEARCH-651.