In an appearance on NBC's "The Tonight Show," Obama said her husband favors Al Green songs -- like the one he sang a snippet of at a campaign event last week ("I'm so in love with you," the president crooned). He also likes Marvin Gaye and Stevie Wonder -- "the classics," she told the affable talk show host.
But, she said, his singing in public came as a surprise to her.
"That was completely spontaneous," she said. "I didn't even hear about it until I heard about it on YouTube.
"He does have a beautiful voice and he sings to me all the time. He doesn't hesitate to show off his lungs to his wife."
The first lady joked that when it comes to such antics their daughters, Sasha and Malia, find "everything we do is highly embarrassing. They just want us to be very quiet."
Leno asked what she thought of the singing voice of Republican presidential hopeful Mitt Romney, who recently led a crowd in "America, the Beautiful."
"Beautiful," she responded. "It is America's song and it's a song that's meant to be sung by every American."