I am way to busy to remember which of 1200+ artists in the collection have been
checked for metadata correctness.

If a checked_date file is in an artist's folder, it means I audited it with kid3
on that date.

If the artist has a home page on the web, its url will be shown below:

# google search parameters: 
#  " albumName " "inurl:playlist" ["artistName - topic"] [+inurl:("/channel/")] site:youtube.com

If an artist, either not knowing any better or having made a conscious decision to release 
their music for free, has created a 'topic' channel on youtube, the url will be shown below: