Ver Cuevana2. 2019 marks the 15th anniversary of Boom, Belgium festival Tomorrowland, and its organizers have a lot planned for the milestone event. Among the special additions for this year's installment is "Symphony of Unity," an orchestral performance which will take place once during each weekend. "Symphony of Unity" is performed by The Metropole Orkest, who famously accompanied Hardwell onstage at his farewell performance in 2018. One 60-minute spectacle took place on July 21st, and the other on July 28th, 2019.