Gestation plays when you are exploring the first cave, and it tells you that you have started an adventure full of emotions. But it's even better when you return to get the Spur, it sounds really nostalgic.
Quiet is Nightmare Fuel, and that's the point. It hammers home that terrible things are happening on the island, the areas that this track plays in being forcibly vacated of their residents being one of them, with one of those areas being Mimiga Village, which has been turned from a bustling Mimiga capital to a ghost town.
The Wii port was criticized for its poor re-arrangement of the soundtrack. So they made a new improved version. Some standouts:
Balrog's Theme is slower than the original version, but manages to make Balrog sound more menacing while still remaining silly.
Gravity. You didn't know what was missing until you've heard this.
Meltdown 2 sounds much, much better in the new fixed rearrangement.
Cave Story 3D has some pretty awesome remixes. Last Cave was already a great piece on its own, but the Cave Story+/Cave Story 3Dremastered version takes the track to whole new levels with an epic sax lead, truly embodying the sheer determination and resilience that was required from both Quote and the player to overcome the game's challenges, both story and gameplay-centric, culminating in a tense but empowering atmosphere leading up to the fight with the Doctor which makes dragging yourself through the Hidden Last Cave in particular so much more bearable.
The remix project, which managed to make them even more awesome. Some standout tracks:
Grass Stains, a remix of the Grasstown theme with some awesome guitar.
We've mentioned Last Battle a couple of times. Now, there are three major versions of the soundtrack: the original, the Wii version, and the 3DS version. All three of Last Battle's versions have their strengths and weaknesses. Here are all three played together.