For macOS 10.10 and later. This script will assist with associating replacement files with a batch of dead tracks. iTunes can perform this task, too, but only one track at a time.
The script will attempt to locate existing files (recursively) in a user-selected folder that have the exact same filenames and extensions as the missing files of a selection of dead tracks. Then, you can determine if the found files are viable replacements for the missing files and the script will perform the replacement. Replacement files remain in their current location and will not be copied/moved to the iTunes Media folder.
This can be a delicate operation. In addition to the must-read documentation included with the script, I also suggest you read what I've written about using this script here.
Checkmarked tracks will have CPR applied. (Additional screenshots are in the read-me PDF.)
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Re-associate batch of dead tracks with files from selected folder