This is now live on railscampteev7.toolmantim.com.
I'm pushing the browser pretty hard with this, so much so it only really works well on desktop Safari.
The sky's a 4-layer background with prime-numbered sized tiles to avoid obvious repetition (I tried 4 layers of CSS-based radial gradient stars, but nothing could cope). It starts at 200% the width of the browser window and is slowly scaled down via transforms. The sounds are synced via the JS events which are fired when different animations finish.
Not quite ready for prime-time browser usage, but it was certainly fun on this little side project.