This is Retrogression: Vol 1, a rock album by musician Stemage of classic video game themes (Super Mario Bros., Punch Out, Ghosts 'n Goblins, and Tetris) performed backwards (Sorb Oiram Repus, Tuo Hcnup, Snilbog n' Stsohg, and Sirtet). I think the Super Mario Bros. theme almost sounds the same backwards as it does forwards. "I don't believe in backwards." I don't even know what that means but I think you might be right!
Keep going for a video of the Super Mario Bros one, followed by the whole album, complete with the reversals reversed so you can hear that too if you're having trouble sleeping tonight.
Thanks to Cameron, who agrees backwards is just a state of mind, or how I put my shirt on today.