Google recently decided to make my life a lot easier by releasing the changelog for Jelly Bean. Cool!
While, of course, I take issue with its thoroughness, it also wasn't all that accurate when it was first published. It's since been corrected, but the internet never forgets. Check out this Google listing:
Yeah... There isn't actually a ringtone editor in Jelly Bean. Google seems to agree, because, after the initial posting, the mention of the editor was completely removed from the changelog.