The book presents unpublished historico-musicological testimonies from the archive of the Constantinople-born Greek musicologist, composer, author, and researcher, Konstantinos Alexandros Psachos. K.A. Psachos (1869-1949) is considered the founder of Byzantine Musicology and Musical Folklore, having left behind an archive of immense historical and musicological value, which remained unpublished for almost 50 years after his death. The book sheds light on unknown aspects of his biography, work, and activities, focusing on three significant events in his life: his upbringing, education, and professional training in Constantinople; his professional relocation to Athens; and the realization of a lifelong goal, the construction of an instrument for Byzantine music (known as the “Panarmonion”) in Munich. The book is illustrated with digitized archival material and includes transcriptions of handwritten Byzantine music documents, letters, and notes by K.A. Psachos in Greek.