What Is a Fugue? How One Musical Idea Travels Between Voices

A fugue usually opens with a subject, a distinctive melody or musical idea presented by one voice alone or clearly enough to stand out. A second voice then enters with the same basic idea, often adjusted to fit a different pitch level. That second entry is called an answer.

As more voices enter, the texture grows. Earlier voices do not simply stop while waiting for the subject to return. They continue with new material, sometimes including a recurring countersubject designed to work against the subject. This layered independence is central to a fugue.

The opening series of subject entries is often called the exposition. Unlike the exposition in sonata form, it is not mainly about presenting two contrasting theme groups. In a fugue, the focus is on establishing the subject across the participating voices and showing how those lines can coexist.

After the opening, the subject can return in different voices and keys. Between these entries, composers often write episodes that develop fragments of the subject or use sequences to move the harmony somewhere new. An episode can create contrast without making the piece forget its main idea.

This is why a fugue cannot be reduced to 'the same melody repeated'. The subject may be shortened, stretched, shifted, combined with itself, or placed against other material. A composer can create enormous variety while keeping the listener connected to one recognisable source.

Some fugues use devices such as stretto, where a new subject entry begins before an earlier one has finished. Others may present the subject in augmentation, with longer note values, or diminution, with shorter ones. Not every fugue uses every technique, so these are possibilities rather than a checklist.

Start by listening only for the subject. Hum or tap its first few notes, then notice each time a new voice takes it up. Do not try to follow every line at once. Once you can hear the subject entries, the surrounding counterpoint becomes easier to understand.

Then notice how many voices are active and whether the subject appears high, middle, or low in the texture. Instruments can make those layers easy to separate, but a keyboard player can also perform several independent voices at once. A score often makes the structure visible because each line can be traced separately.

A clear explanation of a fugue should mention subject, answer, multiple voices, and counterpoint. Those ideas tell you more than simply calling a fugue a complicated piece. Its complexity grows from a very organised process of sharing and transforming one musical idea.

The answer usually enters a fifth higher than the subject, placing it in the dominant key. If the answer copies the subject note for note at that new level, it is called a real answer. Often, though, an exact copy would pull the music too far from the home key, especially when the subject begins by leaping between the tonic and dominant notes. Composers then adjust one or two notes, producing a tonal answer that keeps the melody recognisable while holding the key centre steady.

Johann Sebastian Bach is the composer most closely linked with the fugue. His Well-Tempered Clavier contains two books, each with a prelude and fugue in every major and minor key, making forty-eight in total. His late collection The Art of Fugue explores the possibilities of a single subject and was left unfinished. Fugue did not end with Bach. Mozart, Beethoven and many later composers wrote fugues, and fugal passages, sometimes called fugato, appear inside larger symphonic and choral works where a composer wants a sense of building energy.

The word fugue comes from the Latin fuga, meaning flight, which suggests one voice chasing another. That makes it a close relative of the canon and the round. In a round such as Frère Jacques, every voice sings exactly the same melody, starting at different times, and the music never changes from that pattern. A fugue begins with a similar chase, but after the opening entries the composer is free to write new lines, change keys, break the subject into pieces and decide when it returns.

For this reason, many musicians describe fugue as a way of writing, a procedure, rather than a fixed form like sonata form. Two fugues by the same composer can have very different shapes after their expositions. Some go further than a single subject. A double fugue works with two subjects, which may be introduced separately and later combined, or heard together from the beginning. Hearing two independent melodies fit together, each still recognisable, is one of the special pleasures this kind of writing offers.

In German note names, B means the note English speakers call B flat, and H means B natural. That lets the letters of Bach's surname be played as four notes: B flat, A, C and B natural, a small, twisting chromatic figure. Bach wove this motif into the final fugue of The Art of Fugue as a new subject, and the manuscript breaks off not long after it appears. A note later added by his son claimed Bach died while writing it, though modern scholars doubt that story. Later composers paid tribute with the same motif, including Robert Schumann in his six fugues on the name of Bach.

Composers also transform a subject by inversion, turning it upside down so that every rising step falls and every falling step rises by the same interval. The rhythm stays the same, so a listener can still recognise the shape, much like a reflection in water. Bach used inversion constantly in The Art of Fugue, and two of its pieces are mirror fugues, in which the whole texture can be flipped so that every voice is inverted and the music still works. Listening for an inverted entry is a good next challenge once you can follow the ordinary subject, because the rhythm gives it away before the pitches do.

A good first fugue is Bach's Fugue in G minor for organ, often called the Little Fugue to distinguish it from a longer one in the same key. Its subject is a long, singable melody that is easy to remember after a single hearing. It enters four times in the exposition, each voice a little lower than the last, and the final entry is played on the pedals by the organist's feet, so the deepest voice arrives last with real weight. Because the subject is so clear, you can keep tracking it through the episodes that follow.

At the opposite extreme is Beethoven's Grosse Fuge, or Great Fugue, for string quartet. He wrote it in 1825 as the finale of his String Quartet in B flat, Opus 130, but early listeners found it baffling, violent and exhausting. His publisher persuaded him to write a lighter replacement finale, and the fugue was published separately as Opus 133. Its jagged rhythms and harsh clashes still sound startlingly modern, and many listeners find it hard going. Comparing it with Bach shows how flexible fugal writing is, since the same basic procedure can feel either graceful or ferocious.

A fugue is a contrapuntal composition in which a main subject enters in one voice and then appears in others, surrounded by independent musical lines. Answers, episodes, countersubjects, and later subject entries create variety. Follow the subject first, and the larger structure becomes much easier to hear.