In 1996, Jonathan Larson died the morning of the first preview of his landmark musical “Rent,” and he never got to see it become one of the longest-running shows in Broadway history. Theatrical lore maintains that, during the long silence that followed the show’s debut performance, someone shouted, “Thank you, Jonathan Larson,” from the darkness of the theater. It was a simple sentiment, but it seemed to neatly encapsulate the feelings “Rent” has inspired since it premiered. This weekend, the Modern Theater honors Larson’s legacy with a concert that showcases the music of “Rent.” Directed by Troy Nickerson, the show should demonstrate exactly why Larson’s music retains the immediacy and poignancy so many years later.