Which compositional technique uses two or more melodies played simultaneously?

The compositional technique that uses two or more melodies played simultaneously is known as counterpoint. Counterpoint involves the creative intertwining of independent melodic lines, allowing each melody to maintain its distinctiveness while contributing to the overall harmony of the piece. This technique is central to the structure of many musical forms, particularly in the Baroque and Classical periods.

In counterpoint, each melody, or voice, can move independently, providing a rich and complex texture. This contrasts with other techniques like homophony, where a primary melody is supported by harmonies that are subordinate to it. In unison, all voices sing or play the same melody together, resulting in no independent lines. Harmony, while it involves chords and the way notes relate to each other, does not specifically refer to the simultaneous use of multiple independent melodies. Thus, counterpoint is the correct choice due to its specific definition and application in music.