The Pythagoreans were a persecuted sect, sometimes violently persecuted.  They were a threat to traditional religion, like many new sects. Plato’s teacher, Socrates, was famously executed for religious heresy.

“The Pythagoreans realized that when we hear beauty and music, when we hear notes harmonizing, that’s because the notes have simple ratios, like 1:2 or 3:4. So the beauty of music is direct perception of the mathematical order underlying the world. They worshipped that mathematics.”

“Simply put, they were threatening to overthrow the gods on Olympus and put numbers and mathematics in its place. Prior to Socrates being executed, a number of other philosophers were banished or fled because of threats to themselves. It was dangerous in those days to be a philosopher.”

Now it appears that Plato may have hidden secret musical message in his writings.  Read More:  A Musical Message Discovered In Plato’s Works : NPR.