I want to make this random off-topic comment: For years I've been collecting various audio clips, where "environmental" sound (voice, noise, etc.) transitions into music, or vise versa, in songs, movies and TV shows. I've searched the web and the closest term I can find is "diegetic switch", but not quite. Here's the (short) list:
- https://youtu.be/9j9bVl3rfNk?t=29 In The Defenders, repeated piano note transitions into background music.
- https://youtu.be/isZyX1xd1VQ?t=159 (The Great American Nightmare - Rob Zombie)
- https://youtu.be/pU_mZ1X69Ho?t=364 (Out of Control - Miraculix)
- Justice League the movie where the song "Everybody Knows" transitions into the ambulance siren. Sorry I can't find this footage.