The Soulspace (精神世界, seishinsekai?, lit. "Spiritual/Mental World"), also called the Soulscape in the localized version of Ar nosurge: Ode to an Unborn Star, is the world that exists within the hearts of every living creature. Scientifically speaking, it could be defined as the agglomeration of Static H-Waves that gives form to the individual existence of each being.
In the case of Ar tonelico, while every creature possesses a Soulspace, they can't be accessed unless they are Reyvateils. This is because the Dive technology existing in Ar Ciel is only made to get access to a SH Server and give access to the address belonging to a Reyvateil, as long as she is connected to a β-6D Server, and because the research into mapping out a human mind so it could be possible to Dive into them was never completed due to the Grathnode Inferia. Such Soulspaces receive the name of Cosmospheres, and Diving into them is the act of interfering the waves forming them in order to cause an emotional impact on the Reyvateil, which will then take on the form of a new Song Magic.
In the case of Surge Concerto, the Soulspace receives the name of Genometrics, and aside of being the individual Soulspace of a person (which is specifically called Qualia or Soulspace Address), it is also the place where the Genom they have established a pact with (if they have done so) resides inside their brain. Regardless of the presence or absence of a Genom, this place allows them to craft Song Magic for use through a Genom they have Synchronized with, or through a Cielnotron or a similar vacuum tube device.