In Pirates of The Caribbean: At World's End, the opening scene is of a large group of people queuing up to be hanged. A few people are hanged at one time, and the last set we see includes a boy of about 10, holding a coin. Before he is hanged, he starts singing 'Hoist the Colours High', a pirate song.

When all those doomed to die sing along, some announcer goes up to Lord Beckett, who is sitting at a table and says "They've...started to sing." And Beckett says "Finally."

Why did he say this? Was he waiting for them to sing? From the scenes, I thought he was hanging the people because they were suspected of pirate activities. But the song seemed important somehow to Beckett. What's going on?