This game was a challenge, and I was so happy when I beat it. It's a bit frustrating since it's a wide open field but you're stuck in this one ordinary spot in a field... but that's the whole gist.
Pardon me for going into spoiler territory, but I read the comments section after beating the game and people weren't able to finish, so I actually made this account to help out a bit.
...so yeah, if you don't want hints, you probably don't want to look at the rest of this post.
Still here? Okay.
You're a turtle on its back. You can't turn yourself over by yourself, so you'll need a little help. Maybe you can sense the presence of other things around you. Are you listening?
You can't call for help, and can't sing, but the game will tell you the four sounds you can make. It's more important than it seems, and each sound is different.
Finally, once you have a new object to interact with, you're very close to getting yourself rightside-up again. It'll give you the leverage you need, but not by rocking or wiggling. Grab it and dig into that earth!