"Your Best Friend"[1] is a song composed by Toby Fox for Undertale. It is a short, NES-inspired tune that plays at the very beginning of the game, during the encounter with Flowey the Flower. It also introduces the player to Flowey's leitmotif, to appear in later tracks near the end of the game.
A slowed down (one 13th of the speed or 0.(076923)x) and distorted version of the track's fifth and sixth bars plays during and after encounters where all monsters in a region have been killed. This variant is titled "mus_toomuch.ogg" within the game files but it's usually refered to as "But Nobody Came" by fans, based on the text that appears on-screen during the aforementioned encounters.
Currently, there are 17 rips of "Your Best Friend" on the channel, including three rips of "But Nobody Came", one rip of the track's equivalent in the Undertale fan game Undertale Yellow and one rip from Kingdom Hearts: Chain of Memories II.