Chaconnes and Passacaglias are related musical forms that are based on a repeated bass line (‘ground bass’) with melodic variations and figuration on top, much like a great many pop songs.
The chaconne likely originated in South America as a suggestive dance, and made its way to Spain in the 16th century. In the early 17th century it was banned from Spanish theatres for being ‘lascivious, dishonest, offensive to pious ears’. The passacaglia appeared around this time in Spain as an instrumental interlude, and first appears in printed form in Italy, where Frescobaldi refined the form as a set of variations on an ostinato bass-line and sometimes mixed the two forms. chaconne and passacaglia, in the same composition. In the France of Louis XIV, the chaconne became an extended dance movement, and usually the closing number, in the grand opéra-ballet, as well as appearing in many instrumental works. Composers in Germany and Austria, including Bach and Buxtehude, included these forms in works both secular and religious.
Still confused? Watch the video on the right, produced by the Musicians of the Old Post.