After Buff tells Gabriel she came and will be going home from the nightclub with Johnny, Gabriel leaves and leaves his accordion with the coat-check girl. However, before sunrise the next morning he and Buff are on his father's boat. He is playing his accordion and she is singing.
When Jim and Gabriel are in the house by themselves talking by the stairs, Jim's body position changes in-between shots. When he is filmed with him and Gabriel in equal perspective, Jim has his shoulders at equal height. When he is filmed as the dominant person in the frame, Jim has his left shoulder much higher than his right shoulder.
When Jim is telling Cora that she is the center of the play, they are seated much closer together in the close-up than they are in the long shots.
Nighttime scenes were filmed during daylight hours using a filter to darken the scene. BUT using this technique left the sky bright and the sky at night is ALWAYS dark and black. Further, using this technique always leaves distant objects distinct with detail, whereas if it really were night, they would have just disappeared into the background and shadows. To illustrate, Buff spots her father through a lightly wooded area at a fair distance, whereas in actuality she would have had difficulty seeing anybody under those circumstances let alone being able to specifically identify him. Such is the advantage of having a script.
While by himself Jim Masters is observing his daughters, ex wife and guests around the fireplace. To distract for attention he has the radio next to him turned on at high volume. He first turns it off by turning the volume on/off knob to the right, clockwise. The second time he does he turns it to the left counter clockwise, properly turning off the radio.
At about 0:33:20 after Jim asks Nan if she's sure she's in love the boom mic shadow passes over Fay Bainter.