There's not much about fugal writing or analysis on this forum. Let's change that, shall we? I'll start with a quick overview of what a fugue is, talk about form in 18th century fugue, then examine a fugal exposition. We will cover the following: Definition of fugue A very quick rundown of the differences between Renaissance, Baroque, and 20th century fugue Structural elements of a fugal exposition Subject (Real) Answer Countersubject Link Bridge "Fugue," from Latin "fuga," means "to flee." We get the word "fugitive" from the same root. Fugue involves multiple voices chasing each other by using imitative counterpoint. The conception and use of fugue has changed several times throughout history. When most folks say "fugue," they are typically referring to the high Baroque style of fugue typified by J.S. Bach. Fugue began in the 16th century as the ricercar (Latin for "to seek," where we get the word "research" from), which involved many themes, had non-imitative sections, and stuck to a small number of tonal areas (entrances only on the tonic and dominant). During the 17th century, the number of themes in fugal writing decreased dramatically until it was winnowed down to a single theme, which we call the subject. Composers preferred to make the entire thing imitative, and gradually worked into other keys. By Bach's time, fugue was the most highly developed process of imitative counterpoint. In the 20th century, fugue has a number of treatments but tends to have a more expansive harmonic scope and may involve any number of techniques from different idioms. Fugues is not a form, but rather a technique or a process. That said, 18th century fugues tend to based on the pattern of an exposition section followed by a body consisting of several episodes and entries. For now, let's focus on an exposition. Fugues have a fixed number of voices. The most common numbers are 3 and 4 voices. Here is what the beginning of a three-voice fugue looks like: I have the subject beginning in voice 2, but the voices can enter in any order. Focus on the subject and answer right now. The answer is the same thing as the subject, just transposed. Every voice will either enter with a subject or an answer. As soon as the last subject/answer is finished, the exposition is over and the body begins. Let's look at the second fugue from Bach's Well-Tempered Clavier, Book 1. The fugue starts at 2:08 in this video: This is the exposition section with only the subject and answer. In general, subjects must either start on scale degree 1 or 5. If the subject starts on 1, the answer will start on 5. If the subject starts on 5, the answer will start on 1. This fugue is in C minor, so you can see that the subject starts on 1. Once the subject is done, the answer comes in in the upper voice. The answer is literally the same exact thing as the subject, but transposed up a perfect fifth. Because all the intervals are the same, this makes it a real answer. (We will cover tonal answers at another time.) There is a bit of space between the first two entries and the third voice in measure 7. Voice 3 has the subject, which is again on scale degree 1. As soon as voice 3's subject is done, that's the end of the exposition. If this were a four-voice fugue, then we would expect another voice to come in with the answer. As soon as the answer finishes, it would be the end of the exposition. Now that we have the basic architecture of the exposition, let's fill in the blanks. The first bit I want to talk about is the countersubject. Technically there are rules to writing a countersubject, such as it has to be invertible counterpoint and be used for motivic material elsewhere in the fugue, but I see "countersubject" being used to mean the thing that happens in the first voice when the second voice comes in with the answer. If you write free counterpoint to the answer, you'll be alright. This stuff can get much more technical, but I like to show that fugue is not some big, insurmountable thing that you need to be a genius to write. In the table I provided, I say that there is something called a link between the subject and answer. A link is an optional bit of music that helps to connect the subject to the answer, because they don't always fit flush. There are two interpretations you can make with this fugue in particular. The first is that this fugue does not have a link and that as soon as the subject is done, it moves on to the countersubject. The other interpretation is that the C in the alto voice right before the soprano's entrance is the link. Yes, a single note. That's how links work. The bridge is similar to the link, but it tends to be more extensive. Why? When you compose the answer, you typically move to another key. The next entry is going to be in the old key though, so you have to modulate back. Bridges are usually a couple measures long. When the third voice enters with the subject, the other two voices should keep going with free counterpoint or something that is motivically related to the subject or countersubject.