I just came across your post about how Apple Music does not delete your local music library, but it just happened to me! I subscribed to Apple Music several months ago. Today I turned off iCloud Music Library via iTunes on my iMac and thousands of songs that I collected over many years disappeared. I definitely did not delete my songs manually, nor did another app delete them. They simply disappeared when I turn off iCloud Music Library. Luckily I have a backup, so can restore my music, but I'd like to make sure this does not happen again. I'd appreciate any insight you might have. Thanks!