Did the "festival" take place in Plakias at the end of September? It was on Sept 27 in 2011, the evening I arrived. I have never seen anything like it. It took the coach over 5 mins to manoeuvre into the parking area by the bus stop because of all the cars and every seafront taverna was full. There was a small stage set up in the area in front of Harakas taverna with rows of tables in front.
As it was 10pm I quickly unpacked and went and had a meal but afterwards (well after 11 pm) I went and watched some of the Greek dancing. There had been copious food and drink (apparently provided by the generous folk of Plakias). Seemed a wonderful atmosphere and experience.
I would have liked to have been there for all of it.
Mike