Ar tonelico
The games introduce the usage of Song Magic in battle that has become unique to the "Ar tonelico" series, and even though the depiction of its usage varies greatly from a game to other, it has a few common elements throughout the series: the party is composed by Vanguards and heroines, and the Vanguards must protect the heroines as they sing their Song Magic and until they can activate it, as Song Magic displays stronger effects the longer the heroines sing it. Additionally, there are times when either ally or enemy Reyvateils will be singing Hymmnos songs, which will become the BGM for that particular battle, demonstrating the importance the Songs have in this series.