Siliconera.com has more news about Ar Tonelico 3 - "Gust's next big game is Ar Tonelico III and it's a PlayStation 3 exclusive. The game stars Aoto, a strapping lad who is accompanied by two reyvateils, Saki, a lab born Reyvateil on the run, and Phinnel, a pure blood Reyvateil. These characters live on a third tower known as Sol Cluster. (Thanks for the tip Bradley!!)
Song magic is still a key feature of Ar Tonelico III, but the battle system has been revised. Players can make custom songs with the R.A.H. system and change the background music in real time. Diving into the minds of your party members, an Ar Tonelico hallmark, returns and just like the other games, the feature is used to procure more songs. It also looks like Gust shifted the game's presentation from 2D to 3D."