Altered Echoes Trophy/Achievement guide for anyone who wants it
Unmissable
Transmitted, Schooled, Trained, Stuffed, Remembered
Collectibles
Children's songs - there are three music box strips in the School. The first one is in the big room you reach with a long rope, on the far end of the room. The second one is in a vent after the toilets, take the left path. The third one is after the first stealth section with The Teacher. After passing the shelf filled with broken Bullies, it's on the left.
Traveler's songs - there are two music box strips in the Train Station. The first one is right after getting into the train, behind a pile of suitcases in the room where the first crank is. The second one is reached through a passage on the floor, in the room where you have to climb the phone line. It's in a locked box, the key is on the table.
Dead's songs - there are two music box strips in the Mansion. The first one is in the vent after you get the match box, take the left path. The second one is found after the Nome open the passage below the stairs. Instead of going below the stairs, go straight ahead instead. You will reach the entrance to the Mansion, the music box strip is on the right.
No more songs - collect all of them.
The Transmission
Chair room - when you go through the first purple doorway, immediately go back and you will find yourself in a different hallway.
Something's wrong - after the first purple doorway, there's a changing staricase. Go all the way up and all the way down. There will be a purple doorway on the way up, but just continue going up until you reach the end.
Wonderful throw! - in the room with a circle of purple doorways, you need to throw a rock into one of them and have it loop through the doorways two more times. I found the third doorway to the left of the entrance the easiest. You just can't throw it at an angle, it needs to be as straight as possible.
The School
Bad memories - on the right wall of the very first room, there's a drawing of the Teacher. Throw a dart at her.
Bully bullied - in the toilet, hit the hanging dead Bully with a hammer.
Model pupil - you have to pass the second stealth section with the Teacher without collapsing the tower of books. It's not hard, you will have enough time if you tap the sprint button.
The Train Station
Communuty service - when you reach the first big room with the cool art, throw all the slippers you see into the trash bin.
Taste of childhood - when preparing food to lure the Guest, throw yourself into the pot.
The Mansion
Cheeeeese - in the very first room, there will be a camera on the ledge of the table you climb. Press the button and get photographed.
A present? For me? - in the room after the first stealth encounter with the Naturalist, rescue the Nome that's in the glass jar on the table.
Rope climbing - after watching the Nome you just rescued get brutally impaled on spikes, you must climb the rope to avoid the same fate. You can usually help yourself with planks, but for this you must only use the rope.
The Music Box
Reunion - after the first encounter with Monster Six, you will find yourself in a room with three headless dolls on the right. There are two heads next to them, and one head in the next room. Put the heads back on the dolls.