The Chinese zither 古琴 guqin (Old zither 琴 qin zither), with strings stretched lengthwise on a flat wooden belly, is a pentatonic heptachord which can be played in three different ways: transversely on open strings, longitudinally by stopping, and also in harmonics (touched lightly on various marked points). Such an instrument, age-old in China, might be a theoretical archetype, which is able to make a contribution to the debate on issues concerning Greek music, something which has remained obscure in relation to the classical Western approach. Indeed, the assimilation “heptachord-heptatonic-diatonic” has ineluctably led most Western theorists to occasional misunderstandings of texts related to tuning, modulation, and the names of the modes. The demonstration is carried out in three steps: 1) a consideration of the seven tunings of the pentatonic guqin zither and their permutation through modulation on the diatonic scale; 2) an examination of the correspondence between musical systems and the Greater Perfect System; 3) a conclusion leading to the question as to whether the specific characteristics of the Chinese guqin were known or unknown by the Greeks. In order to maintain an effective methodological approach, we need to remember that Chinese writing gives different names to the notes, according to the system to which they belong. In conclusion, the hypotheses concerning the supposed exchanges and influences from Asia to Greece are strengthened anew.