The other day I got the city’s brochure for free events this summer in Millennium Park. Since March different components of the season’s programming have been announced, from the rock-flavored Downtown Sound series on Monday evenings to the Made in Chicago: World Class Jazz series on certain Thursday nights. But seeing all of the events listed in one place was kind of mind-blowing. Since opening in 2004 Millennium Park has consistently hosted great music, but this year’s season is far and away the strongest. Even if you didn’t set foot in a single other venue all summer, you could enjoy a full season of excellent, wildly diverse concerts. And every one of them is free.