Echoes are a type of activity available in Alan Wake 2, which is available when you play as Alan Wake. Most of them help advance the game's storyline, but some of them are optional.
Echoes consist of two spheres - light and dark. To activate a certain echo you have to stand in such a place that both spheres line up and the dark sphere obscures the light one.
You can check which echoes you have already collected by visiting the Radio in the Writer's Room.
Casey Billboards #1 - Cold CaseChapter: Initiation 2: Casey.
Casey Billboards #2 - Hard CaseChapter: Initiation 2: Casey.
Casey Billboards #3 - Closed CaseChapter: Initiation 5: Room 665.
Casey Billboards #4 - Final CaseChapter: Initiation 5: Room 665.
Casey Billboards #5 - Worst CaseChapter: Initiation 8: Zane's Film.
Casey Billboards #6 - Murder CaseChapter: Initiation 8: Zane's Film.
Draft One #1 - FBI AgentChapter: Initiation 2: Casey.
Draft One #2 - Bad LuckChapter: Initiation 2: Casey.
Draft One #3 - Murder CultChapter: Initiation 2: Casey.
Draft One #4 - TorchbearersChapter: Initiation 2: Casey.
Draft One #5 - Summoning RitualChapter: Initiation 2: Casey.
Draft One #6 - MarkingsChapter: Initiation 2: Casey.
Draft One #7 - The TreeChapter: Initiation 2: Casey.
Draft One #8 - Something in the AirChapter: Initiation 2: Casey.
Draft One #9 - Alice WakeChapter: Initiation 2: Casey.
Draft Two #1 - Another MurderChapter: Initiation 5: Room 665. When you leave room 665, before you take the elevator down.
Draft Two #2 - Pre-Show RitualChapter: Initiation 5: Room 665.
Draft Two #3 - HauntedChapter: Initiation 5: Room 665.
Draft Two #4 - The DevilChapter: Initiation 5: Room 665.
Draft Two #5 - Room 666Chapter: Initiation 5: Room 665.
Draft Two #6 - The ClimaxChapter: Initiation 5: Room 665. It's in the room 666.
Draft Two #7 - Quid Pro QuoChapter: Initiation 5: Room 665.
Draft Two #8 - Dead TiredChapter: Initiation 5: Room 665.
Draft Three #1 - Thomas ZaneChapter: Initiation 7: Masks.
Draft Three #2 - The Cult of the WorldChapter: Initiation 8: Zane's Film.
Draft Three #3 - Crooked CopsChapter: Initiation 8: Zane's Film.
Draft Three #4 - Nightless NightChapter: Initiation 8: Zane's Film.
Draft Three #5 - Clip of the Lost FilmChapter: Initiation 8: Zane's Film.
Draft Three #6 - Down the ChuteChapter: Initiation 8: Zane's Film.
Draft Three #7 - Death of a CultistChapter: Initiation 8: Zane's Film.
Draft Three #8 - The GrandmasterChapter: Initiation 8: Zane's Film.
Draft Three #9 - TrappedChapter: Initiation 8: Zane's Film.
