Dogsong is the 21st track in the Undertale Soundtrack. It plays during the battle against the Greater Dog miniboss (at 0.95 speed) and in most encounters with the Annoying Dog.
It is composed using the SoundFont of Mario Paint and Mario Paint Composer similar to some of Toby Fox's other compositions such "Karkat's Theme" and "Walls Covered In Blood." However, some notes are too low to replicate in either game. Dogsong and Tem Shop both derive from the same melody, of which is from Enemy Approaching.
A faster version of this song plays if the protagonist decides to spare Sans when presented the opportunity during the Genocide Route while showing the message "geeettttttt dunked on!!!"
In the Dog Ending, where the protagonist only kills the bosses, it plays while Sans explains that "a little white dog" took the throne and the Underground is better than ever. It also plays at the end of Hard Mode when Annoying Dog interrupts and ends the game, to Toriel's annoyance. In the "Dirty Hacker" ending, which can only be achieved by reaching the end by way of altering the game's files, this song plays as well.
A very slowed down, distorted, echo-intensified version of this song is found while fighting Endogeny, one of the Amalgamates. A slightly slower version of the song also plays once Endogeny can be spared.
Trivia
- Since the Annoying Dog is supposed to represent Toby Fox, this is considered as his "theme."