Which term describes music consisting of a single melodic line?

The term that describes music consisting of a single melodic line is "monophonic." Monophonic music features one clear melody without any accompanying harmony or multiple voices. This characteristic allows for a straightforward presentation of the melody, making it the simplest form of musical texture.

In contrast, homophonic music involves a primary melody accompanied by chords, creating a harmonic structure; polyphonic music consists of multiple independent melodies occurring simultaneously, which can create complex interweaving textures; and heterophonic music presents variations of a single melody played simultaneously by different instruments or voices, showcasing different interpretations rather than a unison line. Each of these textures has its distinct musical characteristics, but monophonic is specifically identified by its single melodic focus.