The Deggua is a working liturgical library. Its chants, in Ge'ez, cover the Sundays and feasts of the Ethiopian year, with companion volumes serving the fasts and the Divine Office, and its transmission is a living educational system. Boys enter church schools and progress through years of study, memorizing text, learning the three modes, and finally mastering the notation, the melekket, a system of interlinear signs developed within the tradition in which letters drawn from Ge'ez words cue whole melodic formulas, one of Africa's indigenous musical notations.
The masters of this learning, the debteras, are a distinct order of cantor scholars, neither priests nor laymen, who perform the chant with sistrum rattles, prayer staffs and the slow liturgical movement called aquaquam, so that the great services unfold as sung, swayed theology, drum, rattle and antiphon together. Scholarship reached the tradition in earnest in the late twentieth century, when Kay Kaufman Shelemay and Peter Jeffery published a multi volume anthology of Ethiopian Christian liturgical chant, transcribing and analyzing the system and its history, and manuscript digitization projects now preserve Deggua copies scattered through Ethiopia's monasteries. The tradition they document is not a survival but a practice, sung through the night at every major feast wherever the Ethiopian and Eritrean churches gather.