When I put Claire to bed for the night, we always go through a specific routine. We brush teeth, get pj's on, give whoever is in the house a kiss, read about three books, give everyone in the house another kiss, and then finally, I sing three songs to her with the lights out while we are in her room. I try to mix up the first two songs as much as possible, but I always end with Twinkle Twinkle Little Star. The reason for that is I think it gives her the idea that when the song ends I'm going to put her in her crib and leave the room. I don't have anything to back that up, but I do it anyway. So last night, when I got to Twinkle Twinkle, she started to sing along. Really loud. She's kind of done this before, but never for the whole song, and never with so much feeling! Of course she didn't sing words, she kind of alternated between la-la's and ah-ah's, but she definately had the rhythm, singing short and long notes. And she would even hit the right notes sometimes, but I think this is because she sang the same note over and over.
So you see, my definition of 'singing' is pretty loose, but she was trying, and it was so cute.