To get Pastor Farrelly away from his DJ desk you would need to devise a faked possession.
This is the low-spoiler guide for "Faked possession" puzzle in The Darkside Detective - A Fumble in the Dark. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.