I wasn't familiar with the song Stay by Knife Pony, but I'm glad it's been put on my radar, because it's a great piece of original music. You can check it out in the video.
I found out about Stay because IvoryBrony shared a piano cover of the song. It has a completely different feel, but it's a fantastic piece in its own right. And there's sheet music!
Thanks for sharing, IvoryBrony!