Both movies are on my favorites list. I like that you have to pay attention and think and follow the dialogue to know what is happening, on and off screen. No explosions and crashing cars here.
Claire Trevor received the Academy Award for Best Supporting Actress for her work in Key Largo. I think the clincher was when she had to sing for her drink.
Claire Trevor tells the story that she went to Huston and asked for some voice coaching and help in singing like a saloon singer. Huston said sure, we'll get you some coaching. So she shows up on the set one day and Huston says we're doing the singing scene now. Trevor freaks, goes to Huston complaining she had no been provided any coaching. Huston smiles and says that it will help you in the scene.
Trevor was terrified as she sang the song ("Moanin' Low") in front of the whole cast, and it just tears your heart out.
Huston was right that her fear and lack of experience improved her performance as the character is on the skids and no longer the performer she once was.
Nasty behavior by Huston, terrifying for Trevor... and in the end, one of all time great scene results.