Once Upon a Time
Introduction sequence
Death by Glamour
Mettaton EX's boss fight
Megalovania
Sans's boss fight
Your Best Nightmare
Photoshop Flowey's boss fight
Fallen Down
During Toriel's introduction, After Toriel's test of independence, When Toriel leads the protagonist to her home, After sparing Toriel (Slowed down), After killing Toriel and sleeping in the bed (Slowed down)
sans.
During Sans's introduction, In the room with Sans's sentry station in Waterfall, In the room with Sans's Hot Dog stand in Hotland, In Grillby's, In Papyrus and Sans's House, In Napstablook's snail farm
Ruins
While traveling through the Ruins
It's Showtime!
After Mettaton bursts through the wall of the Lab, Before the jetpack sequence of Mettaton's cooking show, After the Bomb Defusal sequence of Mettaton's news report, During the phone call for the Mettaton Ending (Slowed down)
Undyne
While hiding from Undyne during her first encounter
She's Playing Piano
Outside of Undyne's House right before her hangout with the protagonist
Hopes and Dreams
The first segment of Asriel Dreemurr's boss fight
Bring It In, Guys!
During the credits when all of the monsters are being shown
CORE
While traveling through and fighting enemies in the CORE
Hotel
Mettaton's cooking show, MTT Resort
Another Medium
While traveling through Hotland