Deletion triggers of a downloaded song

[Notius]

Plan

Premium(Family)

Country

 Turkey

Device

ASUS ZenFone 2

Operating System

Android 6.0.1

My Question or Issue

 I have a playlist created, which I set the songs in the list to be auto-downloaded. Today I thought about removing a song from that list, but I couldn't be sure if I needed to delete the certain song manually for it to be remowed from the downloaded songs too(to create a space in my disk you know). Or does the spotify app delete the certain song automatically when it's not in the auto-download list anymore? In which cases does a downloaded song gets deleted?