But the moment they are dismissed from drill every tongue is relaxed and every ivory tooth is visible.

8 seconds sound clip from the Glory (1989) movie soundboard.

You can hear this line at 00:24:09 in the Blu-ray version of the movie.

Quote context

[...]

- The rifles? See to it.

- You're a big buck. You're tough, aren't you?

- You've got a lot to learn. You haven't had a master like me.

- Dear Mother: The men learn very quickly. Faster than white troops, it seems to me.

- They are almost grave and sedate under instruction, and they restrain themselves.

- But the moment they are dismissed from drill every tongue is relaxed and every ivory tooth is visible.

- And you would not know from the sound of it that this is an Army camp.

- They must have had to learn this from long hours of meaningless, and inhuman work.

- To set their minds free so quickly it gives them great energy.

- And there is no doubt that we will leave this state as fine a regiment as any that has marched.

[...]