Since the 1950s, the structure underlying most popular songs has adhered to the same old verse-chorus form of music, with many varying only on a superficial level, imitating each other at a deeper level.
Imitative types of musical structure have existed for centuries. During the Middle Ages, the term fuga referred to any piece of music that used a structure called imitative counterpoint in which a piece of music consisted of two or more "voices" that played off each other, with each voice constituting a single melody or harmony living within the larger musical composition (1). In these fugas, the voices largely imitated each other, yet were introduced at different times throughout the composition, which often resulted in an interesting overall melody.
In the 1500s, Italian music theorist and composer Gioseffo Zarlino observed that the deeper structure underlying fugas had diverged down two different streams, and as such he classified fugas into canons and fugues, each of which bore certain similarities, but showed important differences.
Zarlino identified the canon as a "strict" technique of imitation where the voices tended to closely imitate each other's melody throughout the entire composition, with the first voice called the leader, the second the follower, and so on. Since the follower closely imitated the leader in terms of key and rhythm, the canon essentially consisted of the same voice repeating itself at different intervals throughout the composition.
In contrast, the fugue was a "less-strict" form of imitation where the voices imitated each other to a certain extent, but each voice possessed its own different key and melody, each expressing itself more freely so that the nature of each voice changed throughout the composition. The first voice was called the subject, the second the answer, and so on, and although further voices were all played in related keys, they did not have to follow the same rhythm. A passage of music was called an Exposition, after which came another passage of music called an Episode, which created yet more variations on the musical themes introduced by the Exposition (2). Since it was composed of several similar yet individualistic voices, the fugue itself changed as each voice introduced itself throughout the composition.
German musician and composer Johann Sebastian Bach is widely regarded as the greatest master of the fugue. Many people consider his finest fugue to be The Well-Tempered Clavier, a collection of preludes and fugues in all 24 major and minor keys. However, Bach wrote many other fugues, with one of his shortest and simplest, Fugue in G minor, BWV 578, also known as The Little Fugue, which is often used to illustrate the underlying structure of a fugue. Play this fugue (click on the video to the right); you can hear (and see) the different voices as they are introduced.
The Little Fugue...follow each voice as it is introduced.
So in essence, a canon is merely a technique based on strict imitation, consisting of a leader followed by numerous imitative voices, whereas a fugue is a form, with each voice related to - but still different - from the other.
Even during his time, Bach was not the only maestro of the fugue. His contemporary, German-British composer George Frideric Handel, was also an adept, and is widely regarded as the second-greatest master of the fugue. Although Bach and Handel were both champions of the fugue, their lives were very different. Bach did not travel abroad much, was not at all famous during his lifetime, and wrote his music largely for churches, whereas Handel was a man of the world, was internationally recognized, and often wrote his music for the king.
Handel's musical composition, Messiah, is one of the best-known and frequently performed choral works in all of Western music. The music describes what many people would call "the greatest story ever told," that of Christ. It begins with God's promises as spoken by the prophets, and ends with Christ's glorification in heaven. The concluding section of Messiah, the one that wraps it up in a divine fashion, is a fugue called Amen. As you play this fugue (click on the video to the right), try to listen to the different voices as they are introduced.
Amen...a divine piece of music.
Like the composers that wrote them, the fugues written by Bach and Handel contain voices that live in the same musical structure, but differ in how they express themselves within that structure.
Music For Strings, Percussion And Celesta, First Movement
Beyond Bach and Handel, there exists another renowned fugue written by Hungarian composer Béla Bartók, who may not be quite as well-known as Bach or Handel, but still ranks as one of the most prominent composers of the 20th century.
For sheer impact, Bartók's musical composition Music for Strings, Percussion and Celesta may contain the greatest fugue of all time. This composition uses string instruments, percussion instruments, and a celesta (an instrument that looks like a piano but sounds more like an xylophone). As a result, the First Movement sounds mysterious, eerie, and supernatural...yet there are no words to truly describe it. Listen to the entire fugue (click on the video to the right), which starts out slowly, but builds relentlessly, with each voice introducing itself insidiously and haphazardly, like the pernicious emergence of a nightmarish apparition.
Music For Strings, Percussion And Celesta, First Movement...your skin may crawl on first listen.