Copyright Estimate Tool
https://ehscripts.github.io/LostwaveTools/databaseEntryDates.html
Will provide an estimate from the GEMA (etc.) registration number as to when a work was registered.
Not sure who wrote it actually - I just stumbled upon it. But very useful.
And please keep searching the Horfest leads! Lead buddy is available here: https://chatgpt.com/g/g-X7ndLuSaQ-the-mysterious-song-tms it will even do most of the searching for you (just say 'give me a lead')