In order to analyze, appreciate and comprehend the musical form called fugue, one must first know the various elements that comprise a fugue.
Every fugue has its own individual characteristic, which display a full range of human emotions. From peacefulness and tranquility to anguish and despair. JS Bach used rhythms, motives as well as melodies and harmonic movement to capture all of these human emotions. Bach used the temperaments of the different keys to establish the mood of each prelude and fugue. These same tonalities are also clearly defined in his choral works as well. Bach was acutely aware of symbolism in art and religion and used it extensively in his works and was well aware of the subtle subliminal effect it has on the listener in addition to the harmonic progressions, melodic intervals, rhythmic motives and patterns.
Bach very adept in the understanding of numerical symbolism, used numerical codes in all of his music which had a profound effect on the listener as well.
For example in the prelude in c minor from book I, of the Well Tempered Clavier, for the first thirteen bars there are subtle changes. The first note of the first and third groups are the highest and the first note of the second and fourth groups go below the mordent. At bar 14 there is a change. the melodic notes are now above the mordent.
The number fourteen was a very symbolic number for Bach. It represents his name B-2, A-1, C-3, H-8 which equals fourteen. This was Bach way of identifying himself in the music. Sometimes he did this by having fourteen notes in a motive.
Although each fugue and prelude has its own characteristic based on the melody, rhythm and harmonic progression there are particular attributes that are common in all fugues. Each fugue will have one or several of these common attributes.
• Subject-the main theme announced at the beginning of the fugue and recurring throughout the fugue.
• Answer-the first entry of the second voice
• Codetta-a short connecting passage between the subjects/answers
• Countersubject-a secondary theme with which the first voice may accompany the second voice and recurs along with other subjects and answers
• Exposition-first section of a fugue during which all the voices enter either with the subject or the answer
• Episode-a passage between entries of the subject and answer often occurring with a modulation
• Subsidiary subject-second or third subject introduced and also capable of being combined with the main subject
• Inversion-turning a melody upside down so all existing intervals are replaced by similar intervals
• Interchange-the displacement of two or more melodic lines so the lower part becomes an upper part or an upper part becomes becomes a lower part
• Augmentation-altering the subjects rhythm so the subject is double the length of the original subject
• Diminution-altering the subjects rhythm so the subject is half the length of the original subject
• Stretto-overlapping of two or more entries of subject or answer
• Coda-a passage bringing a conclusion to the fugue
With the advance of tempered tuning, JS Bach was able to compose in multiple keys, which previously had not been used. For the keyboard player of his day this meant one would need to develop greater dexterity and technique to perform works in these new keys with five, six, or seven sharps. JS Bach advanced to form of the Fugue to the highest level, from ‘The Well Tempered Clavier’ The Toccatas and Partitas and with his latest unfinished masterpiece: ‘The Art of Fugue’