There are some piano pieces that are not to be considered “classical music” because they do not have elements of classical music. That is to say, songs that have a harmony that has little more going for it than a formulaic I – IV – V chord progression. Some piano pieces, however, from a musical analysis point-of-view, use diminished, augmented and in the case of one of these pieces, a two chord made into a seventh with a flat fifth! However, I wouldn't say they are jazz (at least not free-improvised like bebop) These are tuneful ditties written in the early 20th century, by various American composers. There is only one of these on the site, the "Rialto Ripples" “Poor Buttermilk” (1921) by Zez Confrey: http://www.youtube.com/watch?v=QYQXucRsiHU “Rialto Ripples” (1917) by Gershwin and Donaldson: http://www.youtube.com/watch?v=I2R0oQH2aXY and “Church Mouse on a Spree” (1936) by Frank Froeba http://www.youtube.com/watch?v=r9bYcWK23KI are they classical or popular?