(noun) a melody or counterpoint sung above the plainsong of the tenor OR (verb) to talk tediously or at length
He in fact pleasures in his own descant interpretations of what is being said.
pretty
turning up at their door to descant on Annagret's ingratitude
the second meaning in this case
Long past the hour when his clenched fists would have given out, they whoop descant to the storm.