There is unique dialogue for interacting and playing specific songs on the giant organ during Chapter 4.
Introduction
After getting the ability to climb during Chapter 4, you are able to access a giant organ.



When you hold down a directional arrow (or not) and press Z, you play a note.
When you hold down C and do the same, you can play a lower octave note.
If you play notes in a certain order (as a song), it’s possible to get unique dialogue. Below are some, if not all, songs you can play on the organ to get said dialogue.
Here is a visual guide to go along with my notes
His Theme
His Theme (Asriel’s Theme) from UNDERTALE
Your Best Friend
Your Best Friend (Flowey’s Theme) from UNDERTALE
Annoy Dog
Dogsong from UNDERTALE
Note: I’m not completely sure if it is Dogsong, but it sounds similar
Note: I’m not completely sure if it is Dogsong, but it sounds similar
The Legend
The Legend from DELTARUNE
Main Melody
Don’t Forget from DELTARUNE
Lost Girl
Lost Girl (Noelle’s Theme) from DELTARUNE
Rouxls Kaard
Rouxls Kaard (‘s Theme) from DELTARUNE
Spear of Justice
Spear of Justice (Undyne’s Theme) from UNDERTALE
Hammer of Justice from DELTARUNE
Hammer of Justice from DELTARUNE
Heartache
Heartache from UNDERTALE
You’ve Got a Friend in Me
You’ve Got a Friend in Me from Toy Story
Chopsticks
Chopsticks by Euphemia Allan
Note: x8 means that the note is played 8 times
Heart and Soul
Heart and Soul by Hoagy Carmichael
Once Upon a Time
Once Upon a Time from UNDERTALE
Dark Sanctuary
Dark Sanctuary (Chapter 4 Theme) from DELTARUNE
MEGALOVANIA
MEGALOVANIA by Toby Fox
SPOILERS!!! 1
The Sheet Music given by the old man
SPOILERS!!! 2
Same thing as the previous song, but played incorrectly.