The system of the eight modi for liturgical music has its roots in oldMesopotamian cosmology and Neo-Platonism, applied to the Biblical imaginaryof Genesis. Thus the eight modi symbolised the seven planetary spheresof the cosmos and the corresponding degrees of paradise, indicating theitinerary by which the human soul is to attain its eternal, glorified destiny. Inthis contribution, we try to demonstrate that the eight modi originally wereonly a speculative theory, developed by Syrian Hellenistic philosophers andtheologians, not by musicians. Only after completing a theoretical form,musicians were endeavoured to provide compositions according to the systemof modality and to mould older compositions into the newly developedsystem. This process, resulting in different forms of modality, was achievedindependently in Syria, the Byzantine world, and also in the West. Latintheoreticians e.g., although having only a partial knowledge of the originaldoctrine composed and adapted their chants to such a theoretical system.
