You can "add" a local track to Spotify yes. But if you are an artist and want your music live for eveyone you need to check out this article.
I don't know where to put this, but can you please make the album Broken Brights of Angus Stone available in the Netherlands? Would be great. Ps. this is the correct album (https://www.youtube.com/watch?v=89VDYGrLzVw&list=PLXpGEWHTsS52YvVfQWrskU4MSmquTHGzX&index=3)
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