For one of the flashback scenes, the actors are dancing at a nightclub, there was no foley or specific sound for us to record as the film crew wanted this scene to be artistically mixed to make it obvious that it is a flashback and not just another scene.
Instead of not recording anything though, we decided to record some random lines of dialogue and conversation to layer over the music, with relevant effects to add to a dreamy feel.
we did this by watching what the actors did while filming, then taking them somewhere quieter and reminding them of some of the things that they said before to get cleaner recordings.