I have two questions on using apostrophe:
Why an apostrophe has been used here after "s" in "The 69’ers’ drummer, Tom Callaghan" while the same thing does not happen after "s" in the "Beatles" in the following sentence? The band was playing the old Beatles songs. (Not ... the old Beatles' songs.)
Why do they say St. James' Park (in Newcastle) but St. James's Park (in London)?!
because the drummer is part of the Aussie band (possessive)
because it was name after St James the Less (possessive)
the difference in spelling might be guessed to be due to
There is an extensive description of the conundrum here.
Note that there was a time when the stadium was spelled "St James's Park".
in your example is being used as an adjective same as in
United Airlines seating chart
It is "a Beatles song" meaning
The song is (sung) by the Beatles
but it would be "the Beatles' contract" with their record company that got it produced.