Last-minute April Fool's mod!
This mod makes one building window in each heist flash with rainbow strobes and play muffled music in the distance (two different tracks included). Usually, the window is located somewhere out of the way, so you need to look around and/or follow your ears to find it.
Affected maps were chosen mostly based on how good I could make it look, so there's a bias towards nighttime maps.
Personally, I think it would be goddamn hilarious to install this, forget about it, and get stunlocked a week later when you finally encounter it.

Sound edits by Malfaltto.

(Note: Cloaker corpse not included.)

Branch Bank (Bank Heist; Gold/Cash/Random)
Art Gallery/Framing Frame (Day 1)
Transport: Crossroads
GO Bank
Nightclub
Four Stores
Ukrainian Job
Election Day (Day 2)
Big Oil (Day 1, Day 1 night variant)
Rats (Day 2)
The Diamond
First World Bank
Counterfeit
Hotline Miami (Day 1)
Midland Ranch
Shacklethorne Auction
Breakin' Feds
...probably some others i forgot

• Custom achievement for finding all of the easter eggs