Why the need for 'improvement' in order to demonstrate the influence of something analogous to natural selection on the diversity of forms songs and tunes can take? It may have been Sharp's (and by the sound of it 1950's ethnomusicologist's) understanding of evolution but it's not the way Pamela R refers to it in the first post and, so far as I recall, it wasn't Darwin's either.

It's not really helpful to speculate about the pebbles crushed to sand in the waves or the offerings of broadside authors that a printer wouldn't waste ink on. But are there no examples of song variants being selected for survival and collection because of the way they fitted a particular cultural or linguistic niche?