Unlike Western notation Byzantine neumes used since the 10th century were always related to modal steps (same modal degree, one degree lower, two degrees higher etc.) in relation to such a clef or modal key (modal signatures). Originally this key or the incipit of a common melody was enough to indicate a certain melodic model given within the echos. Next to ekphonetic notation, only used in lectionaries to indicate formulas used during scriptural lessons, melodic notation developed not earlier than between the 9th and the 10th century, when a theta (), oxeia () or diple () were written under a certain syllable of the text, whenever a longer melisma was expected. This primitive form was called “theta” or “diple notation”.