Previously Charles and Caroline complained vehemently about the noise and clamor of the big city. But now in the same hotel bed the night is completely calm and quiet.
Starting at 29:00 when Charles is playing the harmonica, you can tell he really isn't playing it. He doesn't even move the harmonica for the different notes. He is just moving his hand.
At 31:33 during the dust storm, they make it look like the wind is really bad. There is a leaf in the middle of the road and it isn't blowing away or hardly moving yet a wood barrel goes blowing past it.
When Charles is playing the harmonica, when he stops, for a second the music is still playing, showing that it was prerecorded and not matched.
Mary is wearing long fake nails with pearly nail polish. Although the first American nail salon opened in 1878, it is doubtful that a low income farm raised blind woman would have deemed manicures a functional or necessary expense.
From 10:36 - 11:02 as Caroline is saying goodbye to the children, you can see that she is wearing a modern bra.
At 29:46, Charles stops playing the harmonica and pulls it away from his mouth and the music is still playing for a second.