All music is royalty-free and you can download any piece you like :) There's a full listing of all the music in the game, along with the artists, in the "CREDITS" file in your game folder, and in-game, but just for convenience here's the Artifact piece (which I really like too):
https://freemusicarchive.org/music/Broke_For_Free/Layers/As_Colorful_As_Ever/
I'm glad you're enjoying the game! I hope you continue to have fun with everything I have planned for the future :)