During the sixteenth and seventeenth centuries, composers developed the practice of polyphonic writing known as counterpoint. In earlier periods, meldoies were written first, with harmonies occurring incidentally. Later on, melodies began to be written to fit a predetermined harmonic structure.

The practice of counterpoint culminated in the fugue, a multipart composition with usually three or four (sometimes more) voices woven together with a number of different techniques. A fugue is based around a central theme called the subject. The subject is introduced seperately in each of the fugue's voices, and then varied in different ways, such as the following:

• Inversion: The theme is played upside-down by flipping the intervals.
• Retrogression: The theme is played backwards.
• Augmentation: The duration of all the rhythms is increased, making the theme slower.
• Diminution: The duration of all the rhythms is decreased, making the theme faster.
• Transposition: The theme is moved up or down by a generic interval.
• Tonicization: The whole piece shifts momentarily into a new key.
• Sequencing: The theme is repeated a number of times as the harmony shifts by a generic interval each time.

These techniques are not exclusive to fugues and can be found in most baroque music.