From GameBrew - a wiki dedicated to Video Game Homebrew.
A homebrew Zelda instrument player allowing you to play a variety of songs from Zelda games with a variety of instruments. Also has a free play mode so you can play to your heart's content without triggering any in-game songs!
For simplicity, you may download a pre-compiled release from the releases page. We compile ELF, 3DS, CIA, and 3DSX versions of Orchestrina for your convenience. For the most recent commits you may also download the source code and build using devKitPro (requires citro3d, sf2dlib, sfillib, sftdlib, and portlibs.)
For both versions, you will need an internet connection on your 3DS to download songs on first launch, else you may manually download the source code and copy and data/ into sdmc:/3ds/Orchestrina. Launch with your launcher of choice or from the home menu if using CIA, and enjoy!