Amazing how God works

¹⁹ So Saul sent messengers to Jesse requesting, “Send your son David to me, the one who tends the sheep.”
^20-21 Jesse took a donkey, loaded it with a couple of loaves of bread, a flask of wine, and a young goat, and sent his son David with it to Saul. David came to Saul and stood before him. Saul liked him immediately and made him his right-hand man.
²² Saul sent word back to Jesse: “Thank you. David will stay here. He’s just the one I was looking for. I’m very impressed by him.”
²³ After that, whenever the bad depression from God tormented Saul, David got out his harp and played. That would calm Saul down, and he would feel better as the moodiness lifted.

David was a shepherd, he was not some famous musician or something. God has chosen favour upon him. And i had see that God's plan is perfect. God is in the process of removing Saul as the king and installing David. And this is the time where anointing is upon him. God took away His spirit from Saul and Saul felt terrible, so terrible. Then his servants recommended that he get someone who can play the harp to play the harp, so that Saul would feel better. And David was chosen. All things work for the good of Christ is so true, although God allowing evil spirits to torture Saul, it was for good because if that did not happen, David would not be chosen and He would not become king eventually. This marks the beginning of the epic story of David.

Note that God did not send evil spirits, but took away his glory, allowing evil spirits to torture Saul. The Lord is all good and nothing bad can come out form him.