Many years ago, the House Master of my college residence held a Christmas party, inviting mostly faculty associated with the House but also a few of us undergraduates.
After a period of drinks and snacks, we gathered around a grand piano to sing carols. I told the woman next to me, the date of one of the junior faculty, "I hope you'll excuse me. I love to sing, especially Christmas carols, but I can't sing worth a darn." She smiled politely.
After we finished the second carol, she turned back to me. "A lot of people say they can't sing, but you really can't!"