Originally a slow Italian or Spanish dance in 3/4 time, the passacaglia later came to be a instrumental work in 3/4 based on a ground (that is, a melody which repeats unchangingly throughout while other lines are freely varied). The passacaglia is very closely related to the chaconne, except that in the chaconne, the repeating melody is always in the bass (that is, it is a ground bass).
One of the best known examples of a passacaglia in classical music is the one in C minor for organ by Johann Sebastian Bach, BWV 582. A later example is the finale of Josef Rheinberger's 8th organ sonata. Perhaps the most frequently heard passacaglia, however, is the finale of Johannes Brahms' Symphony No. 4 (although Brahms did not explicitly call it a passacaglia, it follows the rules of one and the repeated figure is based on one found in Bach's Cantata No. 150, Nach dir, Herr, verlanget mich).