"In addition to dominating the city’s summer concert scene by its sheer scope and size—last year, Lollapalooza drew a record 270,000 attendees to hear its 130 bands—the festival wields unequaled power over the Chicago music scene via the radius clauses it places on all of those the acts that play on its stages. These prohibit artists from performing for six months before the festival and three months after it anywhere within 300 miles of Grant Park, which includes concert markets as far away as Milwaukee, Madison, Iowa City, Detroit and Indianapolis."
http://www.wbez.org/blogs/jim-deroga...ortunity-98257
Quote & further talk of the Radius Clause towards the bottom of the page.