The single thing which differentiates melody from a succession of pitches
is the implication of a harmonic context.

This is more subtle than it appears, a melody need not be a musical
thought - it need not be a complete musical sentence.  The difference here
is that a complete musical sentence implies closure.  While most works rely
on melodies that are complete, this is by no means always the case.  Many
of Beethoven's melodies are not complete musical thoughts - but images of
a central thought, a central idea.  Handel's interlocking double fugue
themes are often complimentary - neither one, alone, implies a complete
progression.  Melodic ideas which are open ended have the virtue of being
more flexible for the ends of development and transition.  Melodies which
are too complete in themselves are more difficult to reharmonise.  This is
a problem Berlioz often ran into

To imply a harmony links melody to rhythm as well.  Only in the context of
some rhythmic framework is their the ability to "sense" - that is perceive
and interpret - what the harmonic context is.  Beethoven delighted in
taking common successions of notes, altering their rhythm and producing new
resolutions, that is implying new harmonic contexts with known figurations.

That composers and musicians have to grapple with a basic element of their
art is not a weakness, but a strength, it means that the foundation of the
art is perpetually open to exploration.

Stirling S Newberry
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