The dives, the crossings of the Boundary, are all stitched together into a continuous, concatenated alternative biography.  The Dive Life.

   My Life as An Aquatic Being, as one wag put it to himself one winter afternoon, hanging on a mooring line 120 feet down in Honaunau Bay. The humpback whales' raucous commentary - I understand it all. It is not a language. They never bothered to work out a quantized representation of experience. If it is music, as some say, it is more like jazz than any other. It  is a direct transduction of sensory experience, colored only by the physical properties of the cetecean transducer. Mozart put far too much thought into it. But why do we, the ceteceans, us and the others, enjoy music ?  Why on earth do we expend scarce energy and precious time on this thing that hunts not, nor does it gather ? Let 'Em Download, Then Pass Cursor Over Frame To Start 'Em Playing

There, 120 feet down in Honaunau, it is, to this hypoxic mammalian observer, quite clear. Music trains the critical sensory and cognitive skills of discrimination and pattern recognition, with special (but not exclusive) emphasis on the auditory media.   Music trains us to tell this from that, and to anticipate ( at much greater speeds than are possible with mere cognition) what is to come. 

We enjoy music for the same reason we enjoy sex : the pleasure has us doing things that increase the likelihood of our genes proliferating in space and in time. Or perhaps a properly oriented arrow of time, cause and effect would have us say that organisms which enjoy discriminating and pattern recognizing tend to be better survivors and reproducers than those who do not.