Unlike Fuji Rock, that other Japanese music festival, and which celebrated its 10th anniversary this year, Summer Sonic is still very much in evolution. It's an evolution less stylistic than logistical.
The need to accommodate 55,000 people at any one time in a limited urban space -- namely a convention center and a baseball stadium in Chiba last weekend, called for imagination. In the past, the main Marine Stage offered a variety of major acts, from hip-hop to pop, Western and Japanese, while centering mainly on the kind of heavy rock that tends to go over well in a stadium. This year, though, the Marine Stage acts were metal, hard rock and emo/punk.
The Island Stage, which was banished from inside the convention center to a park near the stadium, was almost all Japanese acts. Most of the fun and spontaneity to be had was on the isolated Beach Stage.