A point relevant to the present set of postings is that the mechanical
rights (i.e., rights applying to a recording) differ somewhat in the
UK and, indeed, almost everywhere outside the USA.  Despite a loud
campaign by pop artists for a significant extension, the rights remain
at 50 years.  In other words, the original production company of a
record or piano roll 'loses' it at 50 years old, and it may subsequently
be used (or copied) by anybody with no permission needed or payment
made for the recording itself.

All of the composition rights remain, 70 years from death of the last
surviving composer right across the EU.  There may be other rights as
well, specifically the lyrics, the roll label and other artwork.  The
length of mechanical rights varies somewhat between countries.

Worldwide, there are "collecting societies" that act on behalf of
rights owners, with a web of mutual agreements to pass royalties
internationally back to their owners.  For a long time in the UK the
Performing Rights Society collected on behalf of performers, and MCPS
did the same for mechanical rights.  These days the two have merged.
They provide exhaustive guidance on all of these issues, including the
ways to make use of copyright material.

Clearly, YouTube has come under increasing pressure to share its
advertising income with rights holders.  I wonder how much locational
nuance any checking software they provide has, or whether it applies US
law to all?

The idea of checking the soundtrack against known ones is crafty, but
seems most unlikely to pick up piano rolls.  You can imagine they have
an endless torrent of videos using standard pop tunes!  You can see
from their tools what a problem this is to them, for instance allowing
a video to have a new soundtrack imposed.

Julian Dyer