Storyline
The game begins as Ziggy, the main character, and Zero, his little brother, are running away from Full House, a Stargazer in the mechanical militia. Full House takes Zero away and is about to kill Ziggy when the Soul Master appears. He uses Ziggy's cube pendant to summon Her Majesty, a soldier-type Tune Trooper. The Soul Master and the Tune Trooper defeat the robots and drive Number 42 and Full House away. The Soul Master then explains to Ziggy that he is a conductor, and can summon and control an army through the music that is on the user's iPod. After 5 years of training, Ziggy starts his quest to find his little brother.
Ziggy starts his quest by heading to Oppenheimer, a city to the North. From there he rescues a robot deserter, which he names Z.E.R.O., due to the large number of zeros in its name. It is noted that the cube pendant resonates when they first meet. He then travels to Full House's tower, where he defeats Full House and rescues Golden Wing, a Superstar who joins Ziggy's party.
After that, Ziggy climbs the legendary Joshua Tree and sees the equally legendary Ship of Fools. After travelling to the Ship of Fools, he finds that the Mechanical Militiamen are created from humans through a conversion machine inside the Ship of Fools. Ziggy then goes to Stargazer Straight Flush's tower, destroying Straight Flush and rescuing an archer-type Superstar, Seattlite.
After that, Ziggy, Z.E.R.O., Golden Wing, and Seattlite head into Metropolis, meet Seattlite's daughter, and go into Stargazer Great Artist's tower. After he is defeated, the Stargazer hacks the network and makes sure that he cannot be rebuilt and that he will die human. Finding the tower devoid of any Superstars, they return to Metropolis and find a Superstar named No Future, who had been hiding in Metropolis.
Once Ziggy reaches the core system, he finds that Z.E.R.O. is not a deserter and has been working for Number 42 all along. Z.E.R.O. leads the party to the final confrontation with Number 42, when he steals the cube pendant, allowing Number 42 to use its power to activate the Network, a collective consciousness which can take control of all living beings in the land of Melodica. Ziggy then proceeds to fight Z.E.R.O.. Ziggy disables Z.E.R.O., and when he is remade by Number 42, the Song of the Unsung is unlocked from Ziggy's pendant. The Song of the Unsung is a song made by conductors of old that disables robots when used. Once Number 42 realizes that he has been betrayed by Z.E.R.O., he unleashes all four Stargazers, and they attack Ziggy. After the battle, Number 42 has merged with the Network, transforming into Ultimate Answer 42 and granting him near invulnerability. Z.E.R.O. uses himself to channel the Song of the Unsung into the Network to make Ultimate Answer 42 vulnerable. While this is happening, Z.E.R.O.'s faceplate shatters and it is revealed that he is really Zero, Ziggy's lost brother. After Number 42 is dealt a fatal blow, Zero sacrifices himself to destroy the Core of the Network for good by channeling his current into the Core. The resulting explosion leaves a crater, seeming to having destroyed Zero. As Ziggy reflects on the destruction and subsequent loss of his brother again, his pendant glows, and Zero's body appears, and springs to life, though without any of his memories.
After the credits, Ziggy realizes that Zero's memories are coming back because of the Song of the Unsung. Then the game ends, as they both walk into the distance, proceeding to sing the Song, hoping to bring Zero's memories back.
Read more about this topic: Song Summoner: The Unsung Heroes