To know fugue deeply is to be acquainted with the element of all reason and consistency in music.
– J.S. Bach
The wiki definition runs…
…a contrapuntal compositional technique in two or more voices, built on a subject (theme) that is introduced at the beginning in imitation (repetition at different pitches) and recurs frequently in the course of the composition.
What that essentially means is you take a line of melody – called a “voice” – and then set it off at different intervals in the music. Rather like the musical rounds in Frere Jaques or London’s Burning, only far more complex, since the voices themselves are constantly developing.
What you eventually weave is a highly dense musical tapestry.
The supreme master of the fugue is J.S. Bach. The form clearly fascinated him, and he continued to composed fugues right to his death. Literally. According to his son he was still composing the ‘Art of Fugue’ on his deathbed.
The music itself just ends in the middle, abruptly. It sounds rather eerie.
Let’s demonstrate the process with the start of a relatively simple four-voice fugue that kicks off Bach’s “48 Preludes & Fugues”, the fugue in C major.
Below I’ve marked each introduction of the four separate voices in blue. Even if you cannot read music, you should still be able to see the shape of this eight-note sequence, and see follow its it is repeated as each of the four voices is introduced:
Bach Fugue in C major Opening
A pianist playing this four-part fugue should make each of these separate four voices uniquely distinguishable from each of the rest, whilst at the same time knitting the sound into an organic whole. And for the composer, allowing yourself expression whilst confining yourself within what are in fact the tightest musical strictures requires a high order of musical insight.
No surprise Bach is the form’s master.
Listen to that Fugue again. Can you hear when each of the four voices enter?
Bach Fugue Opening