What does 1 Samuel 18:10 mean?

The next day, an evil spirit from God came over Saul, and he started raving inside his house. David was playing music for him, as usual, and Saul had a spear in his hand. 1 Samuel 18:10 - Modern Text Bible

(Saul is tormented and unstable, while David tries to help by playing music, but the situation is tense and dangerous.)