Mark Ronson tells the story of how Amy Winehouse insisted on adding an electric harpsichord to "Back to Black" - a sound that broke his self-imposed rule of keeping everything strictly in a 1960s style. He plays the part back over the original demo so you can hear exactly how it sits in the track.
The broader point Ronson draws out is about the instinct to resist a collaborator's idea before you've even tried it. Your first reaction when someone suggests something outside your rulebook will almost always be "that's not how it's supposed to work" - but that resistance is usually the wrong call.
When you're working with someone you respect, try their idea at least once. Being wrong doesn't cost you anything, and if it works, the song gets better. The harpsichord became one of the defining sounds of the record.