Today's Beatles: The Final Beatles Song, “Because”
John and Yoko were staying together at Ringo’s house in March of 1969. It’s there that John wrote “Because,” inspired by Beethoven, as played by his wife.
“Yoko was playing `Moonlight Sonata’ on the piano,” Lennon said to Peter Scheff. “She was classically trained. I said, ‘Can you play those chords backward?’ and wrote ‘Because’ around them. The lyrics speak for themselves; they’re clear. No bullshit. No imagery, no obscure references.”
When I interviewed Yoko in 1992, I asked her about her memories of the origins of “Because.”
“When you really listen to it, ” she said, “you see that he did play the chords backwards at one point but I think eventually it cleaned up a bit into a pop format. So he didn’t use all the chords. But that was the initial inspiration.”
Source: americansongwriter.com