“反复地唱歌”可以翻译为 “sing repeatedly” 或 “keep singing the same song over and over again”（后一种表达更详细地描述了“反复唱同一首歌”这一情境）。
“sing repeatedly” 简洁明了，直接表达了“反复唱歌”的意思。
“keep singing the same song over and over again” 则更加具体，描述了持续不断地重复唱同一首歌的行为。