Which of the following statements is true about fugues?

A fugue is characterized by its polyphonic texture, where multiple independent melodies intertwine, centered around a main theme known as the subject. The subject is introduced at the beginning and is then developed and manipulated throughout the piece, with additional entries of the subject that create intricate harmonies and counterpoint. This technique showcases the interplay of voices, making the polyphonic nature a defining feature of fugues.

The other statements do not accurately reflect the characteristics of fugues. For example, although many fugues may be in a major key, they can also be composed in minor keys. Additionally, fugues do indeed have discernible melodies; the subject itself serves as a clear melodic line that is developed. Lastly, while fugues can be composed for solo instruments like the piano, they are often written for other ensembles and can be found in orchestral works as well. Thus, the correct understanding of a fugue's structure and texture solidifies why the first statement is true.