What happens when half a million Cubans gather under the broiling sun in Havana's famous Revolution Square?
Typically, over the past 50 years, they'd be subject to a rambling, four-hour lecture from legendary communist leader Fidel Castro.
Despite the strict rule not to bring up politics, Puerto Rican merengue star Olga Tanon, one of 14 artists from six countries performing with Juanes, kicked the show off with the event's central message: "It's time to change."
Easy there, Olga. You know how the Castros feel about that word.
So, what was behind the regime's decision to allow this? Did the Fidel Castro's famously charisma-free brother, Raúl, decide to unbutton his guayabera a little? You know, allow the kids to blow off some steam so that frustrations with lack of freedom don't boil over? Or could this be like the "Ping Pong Diplomacy" that brought China and the US back on speaking terms in the 1970s?
Surely, Cuba experts will be reading the tea leaves on this and we'll be bringing you their takes.
But for now, you can sit back and watch the show.
Hopefully, for Cuban musicians, such an event might open a window to express themselves freely, but I'm not holding my breath.
When I was there last summer, I met with a Cuban rapper who dares to criticize the communist system through his music. His music is popular with a young generation disenchanted with the revolution, but every time he gets used to playing at an underground venue, the owners of the bar or restaurant get threatened by authorities. He's run out of places to play, but he says won't stop.