Six-string impresario Eric Clapton cherry-picks a panoply of guitar rock heroes — from B.B. King to ZZ Top -- for this blues-drenched all-day festival held at Chicago’s Toyota Park to benefit the Crossroads Centre in Antigua. Over the course of 11 jam-heavy hours, such greats as Robert Cray, Sheryl Crow, Vince Gill and Jeff Beck range across the stylistic map, with Bill Murray hosting the proceedings and Clapton a masterful presence throughout.