The primitive southern Negro, as he sang, was sure to bear down on the third and seventh tone of the scale, slurring between major and minor. Whether in the cotton field of the Delta or on the Levee up St. Louis way, it was always the same. Till then, however, I had never heard this slur used by a more sophisticated Negro, or by any white man. I tried to convey this effect...by introducing flat thirds and sevenths (now called blue notes) into my song, although its prevailing key was major...and I carried this device into my melody as well...This was a distinct departure, but as it turned out, it touched the spot.