Play folder plays songs not even in my library

[edgylitirmor]

Plan

Premium Family

Country

Ireland

Device

PC

Operating System

Win7

My Question or Issue

Play Folder plays songs that are in the folder AND songs which aren't even part of my library.

I have a folder, Electronic, filled with various playlists, subfolders with more playlists, etc. All bleepy goodness.

I pressed Play at the top-level folder and it plays the songs contained in the folder/subfolders. All good.

However, every 5, or 6 songs, Spotify will throw in a song which isn't even in my library. So far, they've not been entirely outside the realm of my tastes, and have even included artists I'd never heard before and will listen to again.

But, when I click play on a folder, I expect to hear the music in that folder and that folder alone.