What is the term for a counter melody that is sung above the main melody?

The term for a counter melody that is sung above the main melody is "descant." A descant typically involves a higher melodic line that complements the primary melody, adding texture and richness to the overall sound. This technique is often used in choral music, where the descant enhances the main tune by providing a contrasting melodic line above it.

Harmony relates primarily to chords and the combination of different pitches, but it does not specifically refer to an independent vocal line like a descant. A chorale is a type of hymn, usually suited for four-part harmony, rather than a specific melody overlaying another. Counterpoint refers more broadly to the relationship between two or more independent melodies in music, focusing on their interaction rather than specifically identifying a melodic line above the main melody.