On the linguistics front, I remember reading in Peter Farb's little book "Word Play" about a whistled language used in the Canary Islands (no, I'm not making this up). It's intelligible at a range of several miles, over rough terrain. As I recall, the discussion was pretty complex, but it had to do with the more favorable noise-to-signal ratio for messages encoded as intervals between tones, as opposed to phonated language, which depends on taking in a substantial soundstring, then replaying it in your head, in effect, to test which binary contrasts (say, between /b/ and /p/) make most sense with respect to the communication event taking place, and the sense that you've been inferring by means of these feedback loops up till now. Of course, you could be working on and confirming a false hypothesis (resulting in a mondegreen, like the time I was in church, and was sure I heard them singing "By the love with which you live/and the toilet overflows").

I'm guessing this whistled language is capable of a pretty limited range of expression, like drums or smoke signals (both of which, however, are grammatized, not like the discrete catalog of signals used by apes).

Why are there mondegreens in lyrics, but not in tunes?