Eddie Morton, of course.

No hurdy-gurdy there! What you're probably hearing is the shō, a Japanese mouth organ traditionally used in gagaku music of the imperial court.
http://en.wikipedia.org/wiki/Sh%C5%8D_%28instrument%29
http://en.wikipedia.org/wiki/Gagaku

The entire intro section of Courser (and the reprise at the end) is an imitation of that ancient music style. Here's a recording of the most well-known gagaku piece, "Etenraku", to give you a taste of the real thing:
http://www.youtube.com/watch?v=kx1uw4n575M

A complete listing of all the instruments & ensembles I used in the song:

JAPANESE/ASIAN:
Shakuhachi
Dizi
Koto
Shamisen
Ryuteki
Hichiriki 1
Hichiriki 2
Shō

JAPANESE PERCUSSION:
O Daiko Set
Nagado Fortissimo
Taiko Drums
Dynasty O Daiko
Okedo
Chappa
Atarigane
Tsuzumi
Suzu
O-daiko
Gagaku Uchimono
Shime-daiko
Hyoshigi

ORCHESTRA:
Piccolo
Flute 1
Flute 2
Flute 3
Oboe 1
Oboe 2
English Horn
Clarinet
Horn 1
Horn 2
Trombone 1
Trombone 2
Glockenspiel
Orch Percussion
Orchestral Cymbal Rolls
Harp
Harp Gliss
Violins 1
Violins 2
Viola
Cellos
Basses

MISC:
Synth Bass
Flute Spits
Finger Cymbals
Gongs
Shaker Rattle

Play

Really it's just a song using Endless Climb because it's for Rose's Denizen battle but since you asked I'll go the whole personal-fanfiction mile.

Preface:

The marble palace lies in a remote part of the ocean floor. After pushing past the pearly greatdoors, traiapsing through the main chamber and fighting through hordes of powerful monsters, you finally find what you are looking for - The Room. This is the palace's heart, and the last of the challenges that the game presents you with before Skaia.

You bravely step inside, ready for danger.

Song:

0:00

The Room is dry, and lit with a dim, mysterious glow. Ancient runes line the stone walls, and the symbol of Light is engraved in the center of the floor in a show of cruel irony. In the center of the room is a golden ship, filled with holes from years of disrepair. Opals, ancient treasures, and grist pour out of the windows of the vessel. It seems that the horde, for now, is unguarded.

As you approach the center of the room, the dim light fades. An ominous rumbling fills the room. Hundreds of yellow eyes, like an army of little moons, peer angrily out of the holes in the vessel. The symbol of Light in the middle of the room shines a terrible orange.

0:24

Suddenly, the ship bursts open. Gold coins rain from the heavens, as belligerent tentacles tear at the walls of the room from the inside of the ship. Blue water gushes in from the cracks in the wall, and you quickly use your magical needles to sew yourself within an air pocket before you are swallowed up by the rapid current.

0:44

The room is filled with water now, and you are overcome with an odd calm. You can see it now, lit by the crackling of your magic needles, inbetween the glints of treasure drifting throughout the room... a terrifying beast, with the legs of the Kraken, the body of Leviathan, and the mouth of a great white shark.

It is the Denizen.

You raise your weapons and smile.

Welcome to the party, Motherfuckers.

0:52

A terrible battle ensues, with the Denizen putting up quite a fight, even though you are at the highest level. Your attacks to little damage to its strong hide! It utilizes myriad tricks to try and trap you, and has no problem smashing wildly into the walls of its own fortress. Its only goal is to destroy you, and it will stop at nothing to achieve these ends.

1:21

You barely dodge the Denizen's huge figure as he rockets past you, tearing through the ceiling of the fort AND your personal air bubble. As your robe whips wildly about you and your eyes narrow, you realize you cannot do this alone.

1:28

You exit the palace through the freshly made hole in the top, hoping that your backup hasn't bailed on you. You didn't think you would need them. The Denizen pursues you as you swim through rocks and cracks en route to the surface, conveniently provided by the undersea mountain shielding the palace from the behind.

1:47

The closer you come to running out of breath and the closer you get to the surface, the closer the Denizen is behind you. Using your own magical blasts as a last-ditch effort for propulsion, you decide to make a mad break for the surface.

Fortunately, at the same time, a familiar hand is steadying a powerful blunderbuss.

1:58

You and the Denizen break the surface one after another at record velocities, just like that scene in Free Willy. Time seems to slow down.

Jade waves excitedly from her vantage point on land. You give her a nod.

2:11

A powerful blast of flame spews from the blunderbuss and strikes the Denizen in the eye, cracking its rough carapace. The denizen lets out a great bellow as you both descend into the depths once more.

2:14

Blind and filled with unfathomable rage, the Denizen makes a last attempt to tear you to shreds, but all it can smell is its own blood. You decide to take after your mother and clean up. No one messes with Lalonde.

2:38

As the Denizen's corpse sinks to the bottom of the ocean once again, you swim briefly back to the surface and wave back to your comrade. She is delighted to see you. You have learned a powerful lesson about friendship.

2:51

Fistbunp.

The planet is saved.


But there are more...