Long term, science, music, and kindergarten is a difficult combination.  Ear training comes to mind as a possibility.  It takes a long time to learn the distinctions of notes, but you can teach "higher" and "lower" and "octaves" and train your students to pick out the differences.  The "practice effect" comes into play in an exercise like this, so the science of learning is involved.  I think a lot of kids (mine included) have a hard time internalizing the fact of "the more you practice something, the better you get at it."

The science of sound can be taught at the same time, but the notions of "frequency" and certainly "the twelfth root of two" (the multiplier factor for frequencies of adjacent notes on our standard do-re-mi scale).

The science of vibrations wrapped in terms of "how can I get musical notes out of ordinary things?" is worth exploring.  I just pulled a computer memory card (a "DIMM"), not able to find a nice wooden ruler, out of a drawer and clamped the end of it to the edge of my desk with my thumb and forefinger and twanged the loose end.  It make a distinct note.  Then I shortened it, so that less of the card hung out and did it again.  Higher note.  Similar effect with different levels of water in a glass (tap the side of the glass), blowing over the top of a bottle with different amounts of water, different sized boxes in the "Make your own instruments" article.  What is vibrating?

It can take a lot of time for the concept of frequency to sink in.  Likewise for the notion of the practice effect.

Two websites, the Sound Site from the Science Museum of Minnesota  and Wild Music, have some great ideas for projects to do with the kids.  They're described on LearningReviews.com:

http://learningreviews.com/jreviews/Science-Categories/Education/Science/Sound_c145_m55.html