Tā bǎ zìjǐ de demo dài jì gěi le chàngpiàn gōngsī.
He sent his demo tape to the record company.
Tips
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A hybrid loan - English "demo" plus native 带 (tape). Chinese music-industry slang pairs 带 with recording media (磁带 cassette, 录音带 recording tape). Even after physical tapes disappeared, 带 persists for demo recordings of any format.
culture
Used mainly in the indie and pop music scene. A 小样 (xiǎoyàng) is a near-synonym and is more native-sounding; demo带 signals industry or hip-hop/rock subculture speech.