Jazz to me is notable for its improvisation, its exploratory nature, and its eclectic instrumentation. I am not, however, a big fan of purely instrumental forms. I find jazz that uses vocals more interesting, with some exceptions. Kind of Blue is still my favorite Jazz album, mainly because of the amazing contrast of styles by Davis, Coltrane, and Adderly. I also was, at an early age, a big fan of the Oscar Peterson Trio. The female voice seems to lend itself to the improvisational aspects of Jazz, and I like to listen to Billie Holiday, Ella Fitzgerald, and the greatest, Sarah Vaughn. And speaking of Folkies...Joni Mitchell has some great Jazz material in her body of work.