Songs without album are not shown
When a song doesn't have the album set in the tags, it doesn't show up in the artist's view.
I have quite a few individual songs of artists which stand on their own (e.g. one-hit-wonders or a famous song without the rest of the album, ...). They don't have the "album" tag set because it simply doesn't make much sense.
When I open the "Artists" view in Yatse, those album-less songs are not shown. Only songs that have the album tag set are shown here.
I can search for the song title in "Songs", it shows up as expected.
Kodi itself (when I browse it on the TV), shows the individual songs. When I select the artist, I can see the artist's proper albums and in addition, there is an item called "Singles" which contains all the non-album songs. Yatse should probably do something similar to allow access to all songs of artist in a convenient way.
If you are using Kodi 17+ Yatse support that, in the artist song view it shows all songs with correct artist tagged.
In Album view you can change the filter show guest appearances to show albums where an artist just make an appearance.
Before that Kodi API lacks the necessary things.