名詞 descant:

1. a decorative musical accompaniment (often improvised) added above a basic melody
   同義詞：discant

動詞 descant:

1. sing in descant
2. sing by changing register; sing by yodeling
   同義詞：yodel, warble
3. talk at great length about something of one's interest

1. In class he descanted on his favorite writer.
   課堂上他詳細論述了自己喜愛的作家。

des.cant

n.（名詞）
Also dis.cant [ds.-] Music
也作 dis.cant [ds.-] 【音樂】
An ornamental melody or counterpoint sung or played above a theme.
高音部長曲：歌唱或演奏中高于主旋律的裝飾性曲調(diào)或?qū)ξ灰?/br>The highest part sung in part music.
高音部：在唱分部樂曲時音調(diào)最高的部分
A discussion or discourse on a theme.
評論：就某一主題進行討論
v.intr.（不及物動詞）
des.cant.ed,des.cant.ing,des.cants[dμs.k2nt., dμ-sk2nt.]
To comment at length; discourse:
詳論：詳細評論；論述：
例句：
.He used to descant critically on the dishes which had been at table.(James Boswell)
.他過去常常對端上桌的菜肴大加批評.(詹姆斯·博斯韋爾)

Also dis.cant [ds.k2nt., d-sk2nt.] Music
也作 dis.cant [ds.k2nt., d-sk2nt.] 【音樂】
To sing or play a descant.
演唱（或演奏）高音部
To sing melodiously.
甜美地演唱

來源：
Middle English
中古英語
from Anglo-Norman descaunt
源自 英法語 descaunt
from Medieval Latin discantus [a refrain]
源自 中世紀拉丁語 discantus [疊韻]
Latin dis- [dis-]
拉丁語 dis- [前綴，表強調(diào)]
Latin cantus [song]
拉丁語 cantus [歌曲]
from [past participle of] canere [to sing] * see kan-
源自 [] canere的過去分詞 [演唱] *參見 kan-

【引伸】
des.cant.er
n.（名詞）