The way the story is told in the memoir, he bashed a repetitive unrelated simple bit over and over again on a piano to cogitate on the problem and solved it splendidly.
I recall that story as he played "boogie woogie" piano repetitively and somehow that facilitated him finding the right harmony notes! Very interesting.
God bless Linda Ronstadt btw....
It's in the Don Was produced I Just Wasn't Made For These Times documentary. It's been awhile since I watched it, but I think she says that he couldn't get the vocal arrangement to "Adios" the way he heard it in his head, and he walked around saying stuff like "just can't get it right", so he walks over to the piano and starts playing a boogie woogie thing in a completely different key, different tempo, different genre, and finally stops, steps to the mic and nails the vocal parts. She was amazed, as I would have been.