The omnibus progression in music is a chord progression characterized by chromatic lines moving in opposite directions. The progression has its origins in the various Baroque harmonizations of the descending chromatic fourth in the bass ostinato pattern of passacaglia, known as the "lament bass". However, in its fullest form the omnibus progression involves a descent in the bass which traverses a whole octave and includes every note of the chromatic scale. It may also include one or more chromatic ascending tetrachords in the soprano, tenor and alto.