I see. There is some controversy about how the Byzantine musical texts have to be interpreted. My mp3s contain some modern ecclesiastical music played with the tuning of George Pachymeres (1242 – 1310). Thats why there is drone.

The intervals in the diatonic tetrachord of Pachymeres are 231-139-128 cents. For comparison in 1881 a commission measured the intervals of the Greek ecclesiastical chant to be 204-168-133 and the traditional Arabic tuning is 204-151-143.