Fugue: An Introduction

For this article I have selected a simple (Hah!) Bach fugue for pipe-organ.

Marie-Claire Alain (1960s) plays: Little Fugue In G Minor, BWV 578

This is a superb performance and hope that you enjoy it!

For those that are interested in the engine

To begin listening to fugue you need to understand four basic ideas: 1) Part writing. 2) The main subject. 3) The counter-subject. 4) Episodes.

It’s not an easy task but it’s well worth the effort!

Part Writing

Fugue is written in “parts”. There are four part “types”. They are the same as their vocal namesakes.

Referring to the image on the left. Those little black dots with lines sticking out of them are the first four notes of our fugue. You don’t have to know what they mean. You do have to know that they are written in the soprano part.

Below them you should see three little black rectangles with coloured circles around them.
These are rests. They just mean nothing is playing in that part – silence. The green circle is in the alto part. The blue is in the tenor part and the red is in the bass part.

As a fugue plays out, its many themes (tunes) will “move” between these parts. For example the four notes that are currently in the soprano could, several bars along, be in the bass with a completely different tune in the soprano. These “parts” are just the pitch at which the tunes (themes) sound. Soprano being the high pitch and the bass being the lowest.  Just as with voices.

As you listen to a fugue you get used to “picking out” the different themes. Fugue is layered. It’s this principal which gives it interest and life.

Tunes, Subjects and Glue

Our fugue has two “tunes”. These are called the subject and the counter-subject. Fig 1 shows the subject of our fugue. It’s the foundation (if you like) of the entire piece.

These five bars are repeated over and over in the different parts to form the whole fugue.

Now, our fugue would be boring on its own so Bach adds a counter-subject that “harmonises” with the main subject. This creates a lot more interest. See Fig 2.

The notes in green are the counter-subject. Again, you don’t have to know what they mean. As you can see the notes in red are the main tune (subject) and the notes in green add a counter-argument – almost trying to out-sing the main tune!

This counter-subject accompanies the subject throughout the entire fugue. Like the subject it too can “appear” in any part. In Fig 2 it appears in the soprano while the subject is in the alto part.

Glue! No I haven’t lost my marbles (well, at least not quite all of them just yet)! Our fugue is in the “key” of G minor. It matters not whether you know what that means. If our entire fugue was “stuck” in this key it would sound pretty dull. So composers like to change to a different key for more interest. To do this in a fugue they can use something called an episode. These are usually short interludes (a few bars long) that allow the composer to get to their desired key. Think of episodes as “glueing together” the various entries of the subject (and its counter-subject).

Don’t panic over this! A simple rule when listening: If you can’t hear the subject playing (in any part) then the chances are that an episode is playing out. Just enjoy and the subject will be along any minute!

Putting the four basics together

OK. Armed with our new knowledge I should be able to give you a quick guide to the opening structure of this fugue.

Bach opens this fugue with the subject in the soprano part (Fig 1). It then answers itself (along with the counter-subject) in the alto part (Fig 2).

So far so good, but Bach has changed key at this point. He now needs to “get back” to his original G minor key so he does this with a short episode.

Once there he now states the subject in the tenor part and then (finally) in the bass. Again with the counter-subject in each case.

Notice what Bach did: The subject was stated in the soprano first then the alto, the tenor, and finally the bass. This is standard fugal practice. If you listen to a lot of fugue you’ll notice it more often. (Bach could have introduced his subject in any order he wished. Example: Tenor, bass, alto, soprano.)

This process of the subject answering itself in the different parts at a fugue’s opening is generally called the exposition of the fugue. It gets the fugue going!

Anyway, that’s the opening complete. Bach then goes on his merry way (the development) with episodes and subject statements to go through different keys until he gets back to the home key for a final statement of the subject in the bass part where the piece concludes with a simple cadence and a G major chord. The end.


Fugue is bloody hard work! Some of the ‘stuff’ that I have written here is not strictly for accuracy but it’s for the sake of simplicity and brevity.

It gets more complicated. There are double fugues (fugues with more than one subject), invertible counterpoint (I’m not even going to try and explain that here), subject augmentation and diminution, less (or more) than four parts, stretto (the overlapping of themes). It goes on… 

I hope that I have whet your appetite and shed a little light onto this fascinating subject.

Next time: Physical Chemistry – The hydrogen atom and its natural resonance. (Use your microwave oven for more details.)

Book suggestions:

“The Music Of Bach – An Introduction” by Charles Sanford Terry – Dover Publications. ISBN 0-486-21075-8

The more serious stuff:

“Counterpoint” by Walter Piston – W.W.Norton & Company . ISBN 0-393-09728-5

“The Study Of Fugue” by Alfred Mann – Dover Publications. ISBN 0-486-25439-9

© Dr Mike Finnley