Pony fans who play low bass instruments (trombone, baritone, and tuba, specifically) are certain to appreciate the work of Erccre147. Erccre147 has shared sheet music for a number of songs from the show, arranged to be played on these low bass instruments. Check out the video for his version of So Many Wonders. I love it—it's like a Flutterguy version of the song.
You can also watch his version of This Day Aria. Then you can take a look at his most recent sheet music, for Art of the Dress. Here's the trombone/baritone version, and here's the tuba version.