Geoffrey Gaskell;

>There is much talk of evolution in music. In general it seems people
>are taking a linear view that Gregorian Chant evolved into polyphony;
>that Renaissance music evolved into the Baroque style and so on.  The
>implication is that each new development is somehow better or more
>approximate to some Ideal Form.  How very Platonic!

There may well be something to the evolutionary model here, but this
does not mean that what is later has to be better.  Even in biological
evolution, the survival of the "fittest" does not mean the same as the
survival of the "best," only the most adaptable.  In music, sometimes
styles change simply because people are tired of them.  If you get down
to the level of individuals, it is likely that many beautiful works of
music, as well as beautiful biological organisms, perish beyond memory.

>A subset of this notion of evolution in music is the notion that
>composition 'y' would be unthinkable without the existence of
>composition 'x'.

This may also be true in some cases.

>Is it not possible that what is perceived by the modern scientific
>mind[set] is nothing more potent than influence? Is it not possible that
>what is perceived as evolution is nothing more that a change in fashion?

Sure.

Jim Tobin