He whistles along with music on the little cartoons the kids watch, such as Dora and Diego. He harmonizes with those songs, as well as little jingles that are on commercials or theme songs from shows. He sings different songs, as he researches things on the Internet or chops vegetables for dinner. He sometimes sings in the shower, and when he's in a good mood, he whistles as he works....literally.
I can always judge what type of mood he's in, depending on if I hear him being musical or not. I love his singing voice. He has one of those types of voices that is unhurried, smooth, and perfectly on pitch. He is not boastful about his voice. He holds it in reverence. He has a talent that I wish I had, but I'm satisfied with being able to listen to him all the time.