Eternal Sonata

This achievement is earned when you complete the second trading sequence during the Encore play through.

Some things of note: All of the strat guides mention the need to talk to the developer in the cave on the left side of Ritardando. The first you can do this is in chapter 5.

They also mention having to talk to the old woman in Baroque. She is outside the main castle entrance on the right of the fountain. Speak to her after speaking with the developer.

Another key piece is photographs. You will need 20 at one point, but you can only carry 12. As long as beat is an option for your party, take 1 picture of every new monster you encounter. You can only hold 12, so try to remember where you took the pics from. This will help later.

Lastly, the earliest you can start the trading sequence is Chapter 6, when you get the ability to warp around from the warp room in Baroque. But you have to finish in chapter 7, when you get to the top of Xylophone tower.

Now, down to business.

1) Defeat Rondo at the top of Aria Temple. You will receive a Heart Pendant.

2) Warp to Forte City. Leave south to travel through Hanon Hills. Enter Fort Fermata from the back. Work your way around to the West side. There's a locked room. Enter it, and talk to Chord. You will earn the "Soul Released" achievement at this point. You give up the Pendant(make sure you do not have it equipped) and receive a Pot.

3) Warp to Tenuto Village. In the house on the right is an old woman. Trade her the Pot for some Goat Stew.

4) Return to Baroque, warp to Agogo Village. Head north to Chorus Plains. Trade the stew to the goat herder for a Coupon.

5) Return to Baroque, warp to Forte City. Leave south and enter Hanon Hills. Find the merchant, and trade the Coupon for Honey.

6) Return to Baroque, head up to the magic researcher in the castle. Give him the Honey. He then needs Agogo Droppings.

7) Travel to Agogo Village. Speak to the little boy to start the photograph hunt. You should have 12 distinct photos on you. Give them to the boy. Now you just need to travel to the last few zones you were in to get 8 more photos. When you have given the boy 20 photos, he will give you Agogo Droppings.

8) Return to Baroque, and go visit the magic researcher. He takes the Agogo Droppings, and makes you spend the night in the Inn. So go sleep it off in the Inn, and return to the researcher. He will then give you Odd Candy.

9) Warp to Forte, leave south, and find the merchant in Hanon Hills again. He takes the Odd Candy and gives you a Glass Ball.

10) Return to Baroque. Head south to the entrance and speak with the priest. He takes the Glass Ball, looks at it, returns it and tells you to take it to the top of Aria Temple.

11) Leave south out of Baroque, work your way through Celesta Forest, back to Aria Temple.

12) Aria Temple is already set with the pathways from before, so just speed past everything to the top floor where you fought Rondo. At the back of the room is a shadow figure. It will take the Glass Ball and turn it into the Orb.

13) At this point, just move along with the story as normal. Teleport to To Coda Ruins. Make your way up Mt. Rock. Enter the portal to Elegy of the Moon. Now you can climb Xylophone Tower. Fight the boss, examine the pillar slot thing at the back of the room. You will place the Orb into it. Go grab your goods. End of achievement.

Note that this guide is not from me, it's just for general information ;) !

To get this, you need to follow a trading sequence started by the achievement "Soul Released." Once you get the orb from Aria Temple and get to Chapter 7, head to Xylophone Tower and get to the top floor. Once there, open the door on the back wall with the orb. Here are the trading locations:

Fort Fermata (Chord): Heart Pendant for the Pot
Tenuto Village (east house): Pot for the Goat Stew
Chorus Plains (Goat Herder): Goat Stew for the Coupon
Hanon hills (Merchant): Coupon for the Honey
Baroque Castle (Researcher): Honey to the researcher who sends you to get Agogo Droppings
Agogo Village (Boy): 20 photos of 20 different beasts for the Agogo Droppings.
Baroque Castle (Researcher): Agogo Droppings for the Odd Candy
Hanon Hills (Merchant): Odd Candy for the Glass Ball
Baroque City (Priest): Tells you to take Glass Ball to Aria Temple
Aria Temple (Final Room): Glass Ball for the Orb