A (20 months) has certain sounds or gestures she makes at appropriate times. Lately, the girls are listening to a lot of Raffi. Every time the farmer "stamps his feet and claps his hands," A knows it's time to clap her hands, too. (I may need to teach her to stamp her feet, too, just because that would be really cute.) She has routines just like that with books; there are pages for making animal sounds and pages for pointing out the moon. Newest development: when we get to the B page in Dr. Seuss's ABC, she says, "Ba ba ba ba." Not that I'm proud of her or anything.
For S (4 and a half), listening to music is more a matter of interpretive dance. She doesn't just happy-tap with Elmo, she emotes with Ernie, clutching her heart and swaying until I am fully convinced that she, like her orange accompanist, does not want to live on the moon. The meanings stay with her, too. Just like with books, she'll bring up questions later that come straight from songs, or she'll sing her own versions, just as she makes up forgivably derivative stories.
So yeah, consider me on the list of people who support the use of music in education. You can put my name right under Will Schuster's.