Here is the full list of all 19 Sylvio achievements worth 1,000 gamerscore. It takes around 10-12 hours to unlock all of the achievements on Xbox One.
You found the museum.
Found all shredded pieces of piano sheets.
Found 116 hidden messages through analyzing the tapes.
Found 80 words in the static.
Used the switch in the terrarium to turn on the lights in a dug up hole.
Found all of Bobby's reels.
Collected all hotel keys from the corpses on the drifting parade balloons.
You shot the crow on the top of the amusement ride.
You blinked a hidden code on the signal lamp, and somewhere the pumps started.
Found 50 words in the static.
You blinked Kristoph's hidden code on the signal lamp.
Found 60 Hidden messages through analyzing tapes.
You blinked a sibling's hidden code on the signal lamp.
Found 30 hidden messages through analyzing the tapes.
Found 20 words in the static.
Played the piano in the auditorium.
You have found 5 hidden messages through analyzing the tapes.
Found 5 words in the static.
Tested the entertainment system in the restaurant.