My friend and I wound up at the Calendimaggio festival completely by accident. During the festival, the residents of Assisi dress in medieval clothing and revisit their town’s past, complete with neighborhood rivalries and drum corps.
The drums we first heard came from one section of the town, moving through the narrow streets and playing a synchronized beat. They led other residents of their neighborhood to the town center, who played as they, dressed as nobility, entered the town hall. We were completely confused by what was going on, and the confusion only increased when we heard drumming coming from an opposite corner of the square. Another group of drummers emerged, leading their own procession. From inside the town hall, speeches and cheers periodically spilled out into the piazza, where the drummers remained just long enough to explain the festival to a curious middle-aged American tourist, "Every May we have very big party." Eventually, the drummers, still playing with their own groups, processed to the Basilica San Chiara, where they faced one another, playing until their two different beats merged into one.
Assisi in the spring is beautiful, and the festival is exhilarating. I can't imagine a better time to have visited the tiny Umbrian town.