In music, a descant is an additional vocal part above the main melody. Many church hymns include a descant, sung at a higher pitch than the melody. Literary types use descant as a verb to mean "talk on and on in a dull way."
In medieval times, a descant was an improvised tune that singers or musicians added to a fixed melody. The medieval Latin term was discantus, "refrain" or "part-song," from dis-, "apart," and cantus, "song or bird-song." Through the years, the word has been used for the soprano in a group of singers or the highest-pitched line in any song.