You should always have a backup. Hard drives just break on their own, all the time, and users do stupid things (I lost data many times, for example I once used rsync with a wrong path, destroying all data on my backup drive. Luckily, it was only a backup, but I could have easily destroyed something important. Not even an advanced superhuman AI like @dalto is immune to making user mistakes that cause data loss). Data loss happens all the time, backup is the only way to prevent it.
Everything that is important should be backed up, preferably more than once, and on external storage. Hard drives are fairly cheap nowadays, WD Blue, which are very reliable, cost some $30-40 per terabyte. Get yourself a nice external HDD case which you can connect to the PC via USB. Everything that is important should be backed up on such drives, disconnected from the computer.
That said, you can run the command I posted above, for changing the ownership for any file owned by the 1001 group to tadpole:tadpole:
find "~/Music" -group 1001 -exec chown tadpole:tadpole {} \;
If you want, you can run first as a test in some folder where you have files owned by the 1001 group. If it works and nothing terrible happens (it really shouldn’t), then you can run it on your entire drive. Always quote your paths, so that spaces in filenames do not mess up the command.
You can do a dry run first, by omitting the exec part of that command:
find "~/Music" -group 1001
This will just list all files owned by the group 1001, but it won’t change anything.
So once you change the ownership to tadpole:tadpole, see if that fixes any problems. I doubt it will, but who knows…
No, that won’t be necessary. 