Her performance embodies a musical sophistication not heard much today in a folk context.
Bossa Nova is a folk song expression by the combination of the African-Brazilian heritage of many Favellas, the poor slum sections of Rio. There is no reason why folk music has to be reduced to basic musical structures. African music is highly complex rhythmically, some of it
un-notatable (if that's word) and yet reflects a kind of folk culture.

I find a kind of musical sophistication when I hear unaccompanied traditional ballads that
subtly reflect earlier modal traces and the bending predictably of tones by singers or musicians.
For example, many Appalachian banjo players, fiddle players or singers who are part of the
sub-culture that came over from Northern Ireland or the Scottish Border will sharp the seventh note of a scale by a few cents. Many blues musicians will flatten the seventh note that suggests a carryover from African modes.