1. What does it mean?
떼창 combines a crowd with singing. It describes many people loudly joining a song at the same time, especially a concert audience singing familiar lyrics back to the performer.
Also written or said as ttechang
2. The nuance
Unlike 응원법, it need not follow a planned sequence of chants. It is about collective singing; no claim about musical precision is implied.
3. Examples
“후렴에서 관객 떼창이 공연장을 채웠어.”
The audience's singalong filled the venue during the chorus.
“가수가 마이크를 넘기자 떼창이 시작됐어.”
The crowd started singing together when the singer held out the microphone.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.