Questions & Answers about Lo de corear el estribillo durante el dúo fue su idea.
Here lo de is a very common Spanish structure meaning something like the thing about..., that business of..., or the matter of....
So Lo de corear el estribillo durante el dúo is not just lo = it.
The whole chunk lo de + infinitive/noun turns an idea or situation into a topic.
Common patterns:
- Lo de llegar tarde = the thing about arriving late
- Lo de Marta = the thing with Marta / what happened with Marta
- Lo de corear el estribillo... = the thing about chanting the chorus...
It often sounds slightly informal or conversational.
Because Spanish often uses the infinitive as a noun-like form.
Here, corear el estribillo durante el dúo functions as a whole idea or action, not as the main verb of the sentence.
Compare:
- Fumar es malo. = Smoking is bad.
- Cantar me relaja. = Singing relaxes me.
- Lo de corear el estribillo... = the thing about chanting the chorus...
So corear here is not saying who did the action directly; it is naming the action itself.