Some bands make it a point to play a radically different set every night. They're called jam bands. In metal and hard rock, that's much more rare. Bands tend to establish a set list and go with it for pretty much the whole tour. But sometimes, a song will make it to the stage at a particular show, and never be played again. Maybe it's because the band's just in the mood to change things up; maybe it's in response to a request; who knows why? But anyway, for this weekend's Spotify playlist, we went to the invaluable website setlist.fm and looked to see what songs some of our bands had played once, and only once...and those were the ones we assembled for your enjoyment. It includes songs by Black Stone Cherry, DevilDriver, DragonForce, Dream Theater, Killswitch Engage, Machine Head, Nickelback, Opeth, Slipknot, Soulfly, Stone Sour, and Trivium.