Singing back at the stereo

Belle loves music, as we've established time and again. She recently seems to have figured out the source of the music. When we play music through our stereo, she looks at the speakers and coos. Tonight, we were listening to a CD while I fed her rice cereal for dinner. In between songs, she looked at the speakers and made cute noises until the music (the next track on the CD) resumed, at which time she gave me a huge smile before taking another bite of cereal.