Please add this great old classic to your library. "Affection," by Ta Mara and The Seen.
Spotify tries really hard to get music available on their service, but in the end the availability of music on Spotify is up to the artist and their music label.This thread by Spotify staff explains why some music is not available:https://community.spotify.com/t5/Content-Questions/I-want-an-artist-song-on-Spotify/td-p/1136005
Music services like Spotify try to focus on getting popular music. Classic music is something different. They have to request it, if they can't get it because of licensing, then that's a different story.