At the bottom of each song’s menu, there’s a button called “CREDITS”. Selecting it will take you to the originals. You can also use “AUTOPLAY” or “TRAIN” to see how it’s supposed to sound when played correctly.
I ordered the notes by the pitch so lower pitches are at the bottom. When developing I tried a bunch of things and this was the most intuitive considering the constraints. It does get easier after some practice.