Just kidding, I didn't put this one on just because it's popular. That's not how I roll. ;)
The context of the song is different depending on whether you're watching the stage play or the movie. In the play, I think that The Friends of the ABC are rallying the people to get all riled up about the revolution (I think), whereas in the movie the song is sung while the students crash Lamarque's funeral and the Revolutionary Funtimes begin. I have to say, I like it's placement in the movie a little better. I think it's very cool how the revolution starts with a whisper and spreads through the people and becomes something very big! Too bad for them it didn't last. Oops, spoilers. :P
Do you hear the people sing?
Singing the song of angry men
It is the music of the people who will not be slaves again
When the beating of your heart echoes the beating of the drums
There is a life about to start when tomorrow comes.
Will you join in our crusade
Who will be strong and stand with me?
Beyond the barricade is there a world you long to see?
Then join in the fight that will give you the right to be free!