How can a single staff show more than one melodic line?

In Western music notation, a single staff can represent multiple independent melodic lines—a technique known as polyphony—by directing the stems of the musical notes in different directions.

This visual method allows each melodic line to maintain its own distinct rhythm and contour while sharing the same five-line framework. By utilizing this approach, composers can notate complex musical textures, such as those found in Renaissance motets or Baroque fugues, ensuring that each voice remains clear and identifiable to the performer.1