Beatles song based on Beethoven?

The Beatles cheerfully sang 'Roll Over Beethoven'. But if Ludwig were not safely out of copyright, his legal team might have had a plausible claim for royalties.

In one of his last interviews, John Lennon revealed how the great German composer provided direct inspiration for Because:

I was lying on the sofa in our house, listening to Yoko play Beethoven's Moonlight Sonata on the piano. Suddenly I said, 'Can you play those chords backwards?'

Structure

The Beatles version retains the key (and key change, as well as the arpeggio pattern) - see here. Lennon also added some bass notes and, of course, a lyric which he claimed was 'clear, no bullshit, no imagery, no obscure references.'

You won't find that kind of language in Fidelio, but there is arguably a similarity of intent across the centuries.