“作为序曲”可以翻译为 "as a prelude" 或 "serving as a prelude"。
"as a prelude"：简洁直接，常用于描述某事物作为另一事物的开场或先导。例如：The concert began with a classical piece as a prelude.（音乐会以一首古典乐曲作为序曲开场。）
"serving as a prelude"：强调“起序曲作用”的动态过程，适用于更正式的语境。例如：The peaceful negotiations served as a prelude to a long-term agreement.（和平谈判为达成长期协议起到了序曲的作用。）