That's the thing where you tie each other up for sexual gratification, right? Like in that Twilight fanfic? 😛

Do they think movies play in real time? What do they think when there's a scene change?

It can't be a montage if they are singing, unless we assume they skipped verses or repeated the song. Either way, I can tell you from personal experience that singing the same song for hours at a time does not make a good date