The chaconne and passacaglia are nearly synonymous descriptions of a musical form that flourished in the Baroque era. The distinctions between the two terms are debated by musicologists, but for practical purposes the terms essentially refer to the same thing: a repeated bass line, or ground bass, over which the composer constructs an ingenious set of variations, which must both follow the framework of the bass and sustain musical interest by creating a sense of forward movement and development. The combination of lulling, predictable repetition and evolving, unpredictable variety makes the chaconne one of the most sensually, viscerally satisfying musical forms ever devised.
Pachelbel's Canon in D is perhaps the most familiar and widely beloved example of the use of a chaconne technique. Over the repeated four-bar melodic and harmonic pattern, the composer uses a melodically elegant three-part canon to create the variations.