The passacaglia is a baroque dance variation form on a short melodic formula usually occurring in the bass. It is similar in form to the chaconne, in which a recurrent bass pattern forms the basis of the composition, implying a recurrent harmonic progression. The two forms are sometimes confused by composers.
Famous examples of the passacaglia include Johann Sebastian Bach's C minor Passacaglia for the organ. Something of the form appears in the last movement of the Fourth Symphony of Brahms, and passacaglias occur in Berg's opera Wozzeck and in Britten's opera Peter Grimes.