What I find I don't like about Jazz is the 'busy' chord structure which detracts from the melody... each to their own!!

To me, jazz tends to involve people competing to see who can disguise the tune the most - and all at the same time...!

;o)

Many trad folk songs/tunes started to evolve at a time when 'keys' as we understand them had not become set in stone, which means they are 'modal' (as suggested by the Countess above).

'The Wraggle Taggle Gypsies' is a good example of a modal tune that sounds minor...