Regarding the "three-chord basic harmonic structure" of the blues, Handy wrote that the "(tonic, subdominant, dominant seventh) was that already used by Negro roustabouts, honky-tonk piano players, wanderers and others of the underprivileged but undaunted class from Missouri to the Gulf, and had become a common medium through which any such individual might express his personal feeling in a sort of musical soliloquy." He noted, "In the folk blues the singer fills up occasional gaps with words like 'Oh, lawdy' or 'Oh, baby' and the like. This meant that in writing a melody to be sung in the blues manner one would have to provide gaps or waits."