Animals "vocalize" or communicate via sound. They also make sounds that accompany tasks in the environment. Those two categories seem to cover just about every scratch and squawk they emit. The same with humans: there is a distinct class of sound that we can call messages as opposed to accompanying sounds of our operations on the environment.

Messages often have surprising complexity and acoustic carriers when analyzed closely. Examples are whistled speech, spontaneous discourse and the variety of gestures we can read.