The song was composed extempore.
这个曲子是即席作成的.
辞典例句
A great poet once wrote an extempore poem here.
一位大诗人曾经在这里留题了一首诗.
期刊摘选
"his ad-lib comments showed poor judgment"
"an extemporaneous piano recital"
"an extemporary lecture"
"an extempore skit"
"an impromptu speech"
"offhand excuses"
"trying to sound offhanded and reassuring"
"an off-the-cuff toast"
"a few unrehearsed comments"
"he spoke extemporaneously"