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:
Wow, growing up in the 80s and thoroughly indoctrinated with musical theatre by my parents... how have I never heard of the Brave Little Toaster until now?
I'm not sure whether I should thank you or curse you. Let's see what my 6yo says.
The article reminds me of Pepe's Burningman operas from the mid 90s... "Devil's Delight, The Fire Tonight" blended into "Devils Do Light The Fire Tonight""
The Brace Little Toaster is a great film, but you might want to preview it yourself before watching it with your kid. There are some scenes of peril and (machine) death that are surprisingly intense for a kids' film and your kid might not handle them well.
Oh man, you're bringing the flashbacks. My siblings watched that movie constantly when I was a kid, and some of those scenes traumatized me for years (I was a sensitive kid).
It's a video game, but Yoshi's Island's title screen (https://www.youtube.com/watch?v=ZkbxyPl83yI) has sound effects which fade out into a musical theme (which adds instruments after the noises stop). It fits cleverly into the SNES's 8 channels of audio which might not have been able to play ocean spray, birdsong, and multiple overlapping xylophone/melody lines at once.
Waves on the shore transitioning into song: Luke the calf - Iona https://www.youtube.com/watch?v=mLx2bKdQIJA - though I'm not sure that one counts as the waves are all through to the end.
- 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.