This side quest can be done during chapters 7, 8, 9, 11, and 12.
In the evenings go to the Galaxy of Terror bar, located in the same section of town as the Sheriffs Office, and speak to Thomas behind the bar who will mention a customer who has been giving them some trouble in the bar when Carol is singing. After being given the side quest come back to the bar again after 9pm on a clear or overcast evening (basically so long as it's not raining) and speak with Jack who is standing to the side near the stage whilst Carol is singing. After speaking with Jack, and then Thomas afterwards, the side quest is finished and you are rewarded with the trophy.
One thing to note, I was attempting this during chapter 7 and on non-rainy evenings Thomas wouldn't go to the bar, instead he would spend the evening with Emily and George at the A&G Diner and then go home. However on rainy evenings the bar still opens and he would go to the bar then. Also, when you go to confront Jack, Thomas doesn't have to be present in the bar, he will appear at the end of the scene when York confronts him though, then disappear again if he wasn't present when York goes in so you don't have to worry about that.