During the flag ceremony at the Japaneses Internment Camp, the wrong bugle call is sounded.
They are lowering the flag at the end of the day, and that is called a "Retreat" ceremony.
The bugle call you are hearing is, "Retreat", which is the first of two bugle calls that are sounded.
When "Retreat" is sounded, it lets everyone know to stop and face towards the flag.
The salute isn't presented until the second bugle call, "To The Colors", begins, as the flag is being lowered.
In this movie, we never actually hear the bugle call, "To The Colors".