Of course we don't know for sure what any of the early, unwritten music sounded like, but the clues are there. The tunes that the Gregorian monks started writing down didn't spring fully-formed from their imaginations - they were very likely rooted in the singing and music of the ordinary people.

And I can't accept the implication that harmony was suddenly invented after - and almost as a result of - the invention of written notation. There will have been simple instruments (bells, tuned percussion, stringed instruments) on which is was possible to play two different notes at once (not to mention massed human voices, of course, which are well suited to this) for hundreds or thousands of years. It seems inconceivable to me that people all over the world would not have exploited these possibilities in many different ways.

The music of primitive peoples - or at least those that were still primitive in the last couple of centuries - demonstrates how people who are musically illiterate are capable of sophisticated harmonies and rhythms, and there's nothing to suggest that our ancestors in Britain and Europe would not have been the same.

Marje