It is believed that the Song of Resonance can only get it by buying it from a specified NPC known as Treasure Hunter Igran Lost Ark Gold. He's found on the Deck Ship that is located on Pleccia island located in the Sea of Gienah. It's situated to the west of Anikka.

Once you've arrived, head toward the southeast of toward the Deck Ship and talk to the Treasure Hunter Igran. The Treasure Hunter Igran will offer you items in exchange in exchange for Pirate coins, such as the Song of Resonance.

It'll cost you around 16,500 Pirate coins, so it's possible that you'll need to do some work prior to purchasing it. If you do not have enough make sure you check your inventory for Coin Chests. The opening of these gives you the possibility of earning various kinds of Coins that you can exchange to Pirate Coins. Just go talk to Traveling Merchants who are scattered in ports. Otherwise, you can use the common methods of getting more, such as quests or daily diaries.

Once you've arrived, head to the south towards on the Deck Ship and talk to the Treasure Hunter Igran Lost Ark Gold for sale. The Treasure Hunter Igran will offer you items in exchange in exchange for Pirate coins, which includes The Song of Resonance.