Joaquin Phoenix spotted filming Joker: Folie à Deux, recorded from someone's apartment window

Joaquin Phoenix was spotted filming Joker: Folie à Deux in LA and people are recording video from their apartment windows. There are rumors this could be a musical, but who really knows as of now. IMDB only says "Plot unknown. Sequel to the 2019 film 'Joker" for the time being. The video was posted by @evanponter on Twitter.