Last year the drought of Cuban musicians obtaining visas to tour the U.S. began to lift, and though so far only a handful of artists from the island have trickled into Chicago, this Saturday Ravinia presents what’s arguably the country’s biggest act, playing one of only three dates in the U.S. The Buena Vista Social Club has become a cottage industry, with hit records, a Wim Wenders documentary, and the juice to make Ibrahim Ferrer and Ruben Gonzalez minor stars. The group’s third main attraction, and the only one still alive, is Omara Portuondo, who’s the featured artist at this weekend’s show.