Chicago, heroes of the ’70s, hits town: Expect plenty of key changes and golden oldies from their horn-heavy, soul pop–gone–soft rock back catalog, including “If You Leave Me Now” and “Hard to Say I’m Sorry.” Sharing the bill are power ballad–specializing late-’70s/early-’80s rockers best known for the swollen "Keep on Loving You" and "Take It on the Run." Bring your lighter (or your iPhone lighter app).
