This chapter describes the story of the panharmonion or Greek organ. It was a pipe organ with a keyboard containing 42 keys per octave, designed to accommodate the non-tempered intervals of Greek Orthodox ecclesiastical music or so-called Byzantine chant. Byzantine chant is a tradition of intermediate orality, where the written and the oral components have worked closely in relation to one another. The chapter attempts to contribute to the existing literature through a portrayal of Konstantinos Psachos as a transitional figure. His collaboration with Eva Palmer Sikelianos on the panharmonion captures a transitory phase in interwar Greece in which competing and, in some ways, overlapping visions, national and cosmopolitan, crossed and interacted. The case of the panharmonion suggests that the two sides were less oppositional and more porous than previously thought. The chapter discusses dominant paradigms in Greek music historiography that cast the musical question in terms of a clear-cut polarity between tradition and Europeanization.