In Remnant 2, you must solve a few puzzles as you travel to different worlds. One of the many puzzles you come across is the Yaesha music box, which is broken when you first encounter it. Before you can complete the Yaesha mainline quest, you must fix this music box.
Remnant 2 offers very little guidance or direction when it comes to fixing this box—or any puzzle, for that matter. You need to find the solution on your own, which made progressing through the game very confusing for me.