[Glathannus]

I don't really know any of the behind-the-scenes trivia about Heisei Fuuzoku, but I know that some "Instrumental" tracks were released, but that they were simply Shiina Ringo excluded from the mix. This means the instruments were/are doing the same thing as the normal album - they're not compensating for the lack of vocals. Also, while the "Instrumental" tracks may have excluded Shiina Ringo's own microphone, her wailing leaked into the microphones of the Saito Neko crew and you can still faintly hear her. She probably had a sound booth rather than a sealed room.

I think pretty much everything you hear in the movie matches the instrumental or regular version tracks of the album, except for Gamble. Now if there are other instrumentals that were never designed to feature any vocals, that would have to be Saito Neko's doing (his violin-playing would replace the vocals). There's a B-side on the KYNK single. Maybe other songs were done the same way, but I have no idea how much time, effort, and recording resources were ever invested into that.