The idea that the Deuteros modes (second authentic and second plagal) of Greek liturgical chant already had a chromatic character before the end of the Byzantine era has gained wide acceptance in the last decades. Trying to go one step further and reconstruct the scales of these modes, the present article attempts a new interpretation of certain crucial passages in late Byzantine treatises, which can provide important clues, if interpreted in connection with the description of the modes in modern Greek music theory and their actual characteristics in the written and oral tradition. The resulting structures can serve as a basis for future transcriptions of chants, at least for the late and post-Byzantine repertory.