In early Greek music theory, an octave species (ε?δο? το? δι? πασ?ν, or σχ?μα το? δι? πασ?ν) is a sequence of incomposite intervals (ditones, minor thirds, whole tones, semitones of various sizes, or quarter tones) making up a complete octave (Barbera 1984, 231–32). The concept was also important in Medieval and Renaissance music theory.