.. How do I open the chest?

Lawrence's journal tells you what to do here. Read the page called "Cave Map" in particular.

As you've probably figured out, is to read through the song for words that represent the different pieces on the lid of the chest, then press them in the order they appear in the song. Read to the end of this hint for a screenshot showing how to do this.

The first step here is to figure out what words each of the pieces on the box represent. Some are obvious, like the broken heart and the wind; others are a little confusing.

The black circle on the top is the sky; the grey square shape at left is a stone wall; the jagged shape at the bottom center is an iceberg; the ocean wave is the sea. The rest are more obvious.

Now read through the song and see what you can find. None of the pieces are pressed more than once, so the first occurrence is the only time you need to pay attention.

Here's a half hint: The first two words are --

-- "sea" and "wind." Can you do it from here?

If this is skunking you, press the pieces in this order:

Sea, wind, bow (of the ship), stone wall, heart, ice (iceberg), grave (says RIP), bone, north (arrow on the compass), broken heart, sail, blackened sky.