A passacaglia is one of the grandest of the old musical forms, which arose in the Baroque era. At its base is a basso ostinato, that is, a short theme in the bass voice that repeats unchanged from the beginning to the end of the piece, while above it unfolds a series of ever more complex variations.
This “unbreakable” repetition of the bass creates a sense of inexorable motion, concentration, and monumentality, so passacaglias often have a dignified, and sometimes tragic, character. They are usually written in triple meter and a slow tempo. An unsurpassed model of the genre is the Passacaglia in C minor by Johann Sebastian Bach for organ. The passacaglia, akin to the chaconne, still inspires composers as a form of deep, concentrated musical thought.
