Descant (noun)

1. A melody sung or played above a basic melody, typically in a higher register.
2. An elaborate melody, typically in a higher register, sung or played above a basic melody.

Origin:

From the latin word "discantus" meaning "to sing in a high voice".

Examples:

1. The choir sang a descant to the hymn.
2. The trumpet played a descant to the melody of the song.
3. The descant was added to the traditional melody to add complexity and interest.
4. The descant was sung by the sopranos while the rest of the choir sang the main melody.
5. The descant was played by the flute and added a beautiful harmonic to the song.