The omnibus progression in music is a chord progression characterized by chromatic lines moving in opposite directions.[1] 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".[2] 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.
They are also known as "chromatic wedge progressions", in reference to their wedge-like appearance in score.[3] The origin of the term "omnibus" (Latin: "for all") to describe such a sequence is unclear, but it is of note that the chord progression encompasses all of the notes in the chromatic scale.