The music library cannot be saved. Unknown error occurred (3851)
doctoraway
User level: Level 1 (8 points)
User level: Level 1 (8 points)Music library fails to save with unknown error 3851
Posted on Sep 29, 2026 8:43 AM
3 replies
sooperfresh
User level: Level 2 (377 points)
User level: Level 2 (377 points)Sep 29, 2026 4:37 PM in response to doctoraway
That message means Music couldn't write its library file, and Apple doesn't document the 3851 code. Quit Music, hold Option while reopening it, and use Choose Library to point it at your Music folder again; if it still won't save, Create Library and add your media folder back in. Or run Katalog alongside the Music app: it's a separate Mac library app that writes your edits into the music files themselves, so they don't depend on Music's library saving. i built it, so grain of salt.
sooperfresh
User level: Level 2 (377 points)
User level: Level 2 (377 points)Sep 30, 2026 12:40 PM in response to doctoraway
Glad it helped. When you first open Katalog it offers your Music media folder, so it reads the song files directly and doesn't need the library file that's failing to save.
doctoraway
User level: Level 1 (8 points)
User level: Level 1 (8 points)Sep 30, 2026 12:00 AM in response to sooperfresh
Thanks for your help.
I will look into Katalog.
doctoraway
Originally posted at discussions.apple.com/thread/256367289