After you get the Siren Instrument from Bottle Grotto, you get a hint to look in Ukuku Prairie for the next instrument.
Give BowWow Back
You can go to Madam MeowMeow's house in town and go inside to talk to her to return BowWow.
After doing this, if you are playing Link's Awakening DX on a system that can play the game in color, you can go to the optional Color Dungeon.
Find Richard's Villa
Go east from the shop in the village. A sign will say that you can go east to Ukuku Prairie. Lift the rocks, then go east. You'll see a warp spot. Go south from there. Keep going south and following the path until you reach a house. Go inside and talk to Richard. Agree to bring him the five Golden Leaves.
Reach Kanalet Castle
Go east from the villa and follow the path. When the path splits, go east. When the path splits again, go north. You will find that the castle is closed. Go east and you will find a monkey asking for bananas. Give the bananas to the monkey. If you don't have the bananas, get the Yoshi Doll from the Trendy Game in the village, then give it to the mother who lives north of Marin and Tarin to get a ribbon, then give the ribbon to the small Chomp that lives in the dog house of Madam MeowMeow's house to get a can of dog food, then give the can of dog food to Sale, the alligator who lives in a house near the beach. He will give you bananas.
Give the bananas to the monkey, and then some monkeys will come and build a bridge. Go up the bridge and you will find a stick.
Keep going north until you find a phone booth. Go west from it and cut the bush to reveal stairs. Go down.
Go west past the Goombas, using the Roc's Feather to jump up the ledge. Go west and jump over the spikes, then jump up to the ladder and climb up.
Get the Gold Leaves
Go east, then south. Kill the Mad Bomber to reveal a Gold Leaf. Take it.
Now go north, west, and south to a screen where there is a bird in the tree. Throw a rock at the bird to make it start flying. Defeat it to reveal another Gold Leaf.
Go south again, then east to reach the castle entrance. Go inside.
In the second room, with the Bubble moving diagonally around the room, kill the two Iron Knuckles and the red Zol to make a Gold Leaf fall from the ceiling. Take it.
Go north and then east to find a button. Step on it to open the castle gate. This way, you can easily go in and out from the castle.
Go north and then west. Go up the stairs.
Go east and follow the path until you are outside. Go into the center door.
Lift the pots. Throw one at the closed door to make it open. If you keep lifting pots, you should find some bombs.
Go north through the door that you threw a pot at, then carefully defeat the Ball and Chain soldier. The soldier will swing the ball and chain more rapidly just before throwing the ball toward you. Approach the soldier to make it spin the ball and chain more rapidly, quickly hit the soldier with your sword, then run out of the way. After you defeat the ball and chain solider, it drops one of the five Gold Leaves.
Go back outside, lifting pots to try to find more bombs. Then when you are outside, go into the door on the left. Follow the path until you are in the room with the Spark going around the walls. There are two Iron Knuckle pictures on the wall. Bomb the one on the left to make an actual Iron Knuckle come out. Kill the Iron Knuckle to get a Gold Leaf.
Get a Shovel
Leave the castle. As Richard mentioned earlier, you are going to need a shovel. You can buy one from the town shop for 200 rupees.
Find the Key
When you have a shovel, go back to Richard's Villa. Talk to him and he will step aside and tell you to push the box, so push it. You will reveal some stairs. Go down. Be sure that you have purchased a shovel from the shop in town before you continue.
In the underground area, go northwest, being careful to avoid the green Zols that are hiding in the ground. In the next room, push the rock up, then jump over the gap and open the chest. It contains a Secret Seashell.
Go back to the last room and take the northeast path this time. Go up the stairs. Go west, then south, and go outside.
You will be in a maze. Cut the bushes to reveal holes and solid ground. Cut the bushes until you can go south to the next area.
In this area, you can either go southeast or northeast. Cut the bushes so you can go southeast.
In the next area, cut the bushes so you can take the northeast path.
From there, cut the bushes so you can take the northwest path.
You will reach an area with an owl statue. Cut the bush in front of it. You can talk to it and it will tell you that there is something in the dirt where you are standing. Use your shovel on the ground in front of the statue (if you don't have a shovel, you will have to go back to the village and buy one from the shop). When you dig, the Slime Key will come out.
Find the Dungeon
Now go back the way you came, through the maze, through the underground passage, until you reach Richard's villa. Leave the villa and go north from there.
You will reach a place with a keyhole. Push on the keyhole to open the dungeon.
To reach the dungeon entrance, go south, past Richard's villa, until you can go west to the lake. Go south along the lake, then jump across to the small island in the water. Walk west, then jump across the other islands. You can go up the stairs and go west to find a diamond of grass, and you can dig in the middle to get a Secret Seashell. Go east and then down the stairs.
Go west from the stairs to reach the dungeon entrance. This is Key Cavern.