via Eric, a wonderful rant on Pachelbel's infamous Canon in D. One of Eric's commentor's asks whether the piece is really a passacaglia rather than a canon, and the answer is yes and no. A passacaglia has a recurring bass line with varied melodies, and Rob Paravonian points Pachelbel's recurring bass line out quite effectively. A canon has multiple parts playing the same melody in imitation, which the upper three parts in Pachelbel's piece do. Fun facts about canons: The melody doesn't have to be in the same key for all the voices, resulting in canons at the fifth or ninth, and it could be played backwards (crab canon) or upside-down (mirror canon). The imitated melody could also be played at twice or half the length of the original, called a mensural canon.