The Hagia Sophia in Constantinople (first a Christian church, then a mosque) and the Mezquita in Córdoba (first a mosque and then a Christian church) have something in common: they both serve as a symbol that it is possible, independently of claims to power, to recognise and tolerate the variants of belief in God with mutual respect for the dignity of man.

Córdoba points to the future, to an interfaith time in which global integration is only possible when one respects those who believe and think differently. Tolerance secures our future.

Robert M. Helmschrott was inspired by these buildings for the two organ works Hagia Sophia and Córdoba.

Ex oriente lux refers to the Patriarch Abraham, the "father of many nations". Abraham occupies a central position in the Tanakh, the Old Testament, since according to tradition the "Twelve Tribes of Israel", and thus also Jesus of Nazareth, were descended from him. The Abraham of Islam and his son Ishmael, in turn, are considered the progenitors of the Arabs and ancestors of the Prophet Muhammad. Judaism, Christianity and Islam thus refer to Abraham as their progenitor.

These three organ works are musically oriented towards historical circumstances. La Fenêtre sur l'éternité (The Window to Eternity) consummates these visions and reflections against the backdrop of infinite reality. Seen in this way, the cycle also has an interfaith dimension. All four works were commissioned by the organist Franz Hauk.