Ar Tonelico OVA is based on the PS2 video game of the same name. I've played the game itself before watching this OVA. The animation itself is on par. What I like is that they used some of anime scenes from the game (only modified a bit). The story itself is not good but not bad either. After watching this, I thought that this was made to show how the magics are done and show in depth one of the places found in the game. Just my thoughts. Really. I do like the characters a lot. Sadly, only some characters appeared but managed to retain some of itstraits and behaviour.
I'm happy that they used some of BGM from the game and retain the characters' seiyuus. The hymns frequently used in Ar Tonelico games is certainly unforgettable.
I recommend this to anyone who either have played the game or not. Poor thing that this is only a one-episode OVA. If it turns into an anime series, it would be a hit.