Rule 1: Still available in the same or (1b) similar form direct from the/an original artist.
Rule 2: Available from a third party, with reason to believe the artist is fine with this.
Rule 3: So famous that it would be plain silly to leave it out.
Rule 4: Being unlisted is not, on its own, grounds for exclusion.
The first three editions of "Sounds of 2014" had no skipped entries at all. This time, we're not so lucky. I did have to think about one song before deciding it justified a Rule 3 application, as you'll read below. The final entry, though, I felt fell the wrong side of the line, so it's not here. Sorry! Here's the list:
85: General Mumble – Couldn't You Just Simply Die?
84: Forest Rain – Nightmare Night
83: Sim Gretina, EileMonty & Copper – Moving On (cover)
82: Turquoise Splash & Megaphoric ft. Joaftheloaf – The Twilight Will Rise
81: skipped
As usual, if you come with me beyond the jump break, you'll get a YouTube embed of the relevant songs, together with a paragraph of my comments and thoughts about each of them.