A period of deep isolation in my late 40s gave me reason and opportunity to learn accoustic guitar. No lessons, no sheet music, no theory; just chords swiped from established songs. I found my first 'round' [G, Em Am, D] in the appropriately named fiddle tune; Poor Old Wayfaring Man of Grief.
Like Stephen King describes in On Writing, these creative works arrive as a bright flash; a premise or a phrase that immediately feels fully-formed, yet very well hidden. Uncovering and assembling the pieces--the words, the chords, the story, the strum--becomes an obsessive journey that doesn't end until it's secure on the page.