@Deb, Sneaky & Orly

That's the problem:
there are two variants of the screen test with the various actors posing for the camera in their own little promos (or together),
one variant plays Hopkins's Trouble BLues whereas
the other plays my mystery song.
Although Trouble Blues is listed as the song under my variant, if you listen to the two songs, it's clearly not the same.
I'm so stumped.
This has never happened before: not to be able to find a song by its lyrics...

Thanks for keeping a lookout. If you happen to come across it I shall be forever grateful.