Change
Death.
It's the one thing we can be sure of.
Change too, I suppose.
If you were to visualize a tree with change at its base/trunk, branching out in degrees of change, I always figured death might be next in line after change itself. In some sense all change comes in the form of the death of one thing that gives way to another, which points us to the inextricable, inexorable link between death and birth.
Death comes in lots of forms. Human death is the great change that frames our lives. In some ways it is equaled by birth, but the peculiar thing about birth is that we never ask to be born, and we're not conscious of our own birth in the same way we our own impending death.
Music is in the business of change, and in that sense in the business of death and birth. We often think of creation only in terms of birth, but as soon as something is born it casts the shadow of death.
Change itself has no intrinsic value. It can be subjectively good, bad, or benign, but in and of itself it is a descriptor of an ongoing process that we sometimes break down into individual events, most often points of inflection that represent a greater degree of change. It's part of the way we compartmentalize change, in degrees of change, from little change to big change. Death falls at the big end of the spectrum.
Musicians also deal with degree of change, because it's music is created by manipulating the status of a sound through pitch change or rhythmic change. Juxtaposing many changes at once we get music, and structure in music, both improvisational and compositional, is about layers of change. Within a verse there are chord changes, melodic changes, and then there's a separate bridge that represents a macro level change in the scope of a song.
Part of making good music is not only understanding change itself, but also the way we experience musical change as listeners. That of course is all wrapped up in the managing of musical expectations, a topic approached in studies of musical phenomenology.
Anyone who composes for improvising musicians allows change to exist as a variable element within a larger structure. The extent to which that structure is or is not changing and fluid itself is yet another factor in the layers of change present.
To paraphrase, Alan Watts once said that human beings try to make a wiggly world straight. Music at its best, instead of making a wiggly world straight, represents life in all its wiggly glory.