George Harrison rarely strayed from his guitar, but he did for “Old Brown Shoe” twice. He wrote the song on an instrument he barely knew how to play and then added bass to the track in the recording studio.
In his 1980 memoir, I Me Mine, George said he wrote “Old Brown Shoe” on the piano, an instrument he wasn’t very familiar with.
“‘Old Brown Shoe.’ I started the chord sequences on the piano (which I don’t really play) and then began writing ideas for the words from various opposites: ‘I want a love that’s right/ But right is only half of what’s wrong.” Again it’s the duality of things–yes-no, up-down, left-right, right-wrong, etc.”
During an interview with Creem Magazine, George said he liked playing the bass.
He said, “But I do: I think bass is a good instrument because, even without being clever, the part of the bass is really important in the way it holds it all down with the bass drum. I like a bass when it doesn’t get in the way of anything.
Source: cheatsheet.com