songs missing under artist

All songs need an Album, Artist and Title.

so, if there is no album, it will not be displayed under the artist?
Maybe.
Seems to be a bug in the most recent versions.
If you have songs from one album and songs with no album, the songs with no albums will not show up under Artist.
If you have songs from more than one album and songs with no albums, all songs will show up under Artist -> {Artist name} -> All.

Yes it would.
Later, if you decide to put the actual album names, you can create a smart playlist looking for album Unknown.

It would show you all albums with a name of Unknown when/if you wanted to put an actual album name on the songs.