I created a new iTunes library on a hard drive and the one of my computer got overwritten - how do I retrieve it?

Hello pa93,

If you have a Time Machine backup, you may be able to reinstate your prior iTunes Library using the steps below:

1. On your Mac, open a window for the item you want to restore.

For example, to recover a file you accidentally deleted from your Documents folder, open the Documents folder.

If you’re missing an item from the desktop, you don’t need to open a window.

2. Use Launchpad to view and open apps on Mac and open Time Machine (in the Other folder). A message may appear while your Mac connects to the backup disk.

3. Use the arrows and timeline to browse the local snapshots and backups.

If you see a pulsing light to semi-dark gray tick mark, it represents a backup that’s still loading or validating on the backup disk.

4. Select one or more items you want to restore (these can include folders or your entire disk), then click Restore.

You can also find those steps in this resource: Restore items backed up with Time Machine on Mac - Apple Support

Hopefully that puts you on the path to getting your prior library back.

Take care.