This is quite fun to play around with! Many of the other CA-based music generators I've seen have sounded rather atonal and random compared to this one. Here's one I made using symmetric initial conditions (doing this makes for somewhat interesting visual patterns as well): http://www.earslap.com/projectslab/otomata?q=0q1q2q3q8w8y8p8...
That's partially the result of the chosen scale. Run a set of "up" arrows from the top left to the lower right and it will play the scale. Then go back to just playing around, and you'll hear how that choice colors the results. A different scale choice would have different results. This would combine well with bajsejohannes's idea; you could exert some control over the scale while letting the automata run free.