Pritzker Pavilion in Millennium Park

"Great place for free music and a picnic"

The Chicago Symphony Orchestra has a summer concert series during (surprise) the summer months with evening concerts. BUT they rehearse during the day, between about noon and 2 pm. Bring a picnic, sit on the lawn and listen to a CSO concert, then run around under the Bean (Cloud Gate) or go play in the fountains.

The pavilion was designed by Frank Gehry and is worth a look even if there's no music.