UNDERTALE Soundtrack is the soundtrack album for Undertale, released September 15, 2015, and available for purchase from Bandcamp, Steam, and the game's website. All tracks are composed by Toby "Radiation" Fox.
There are 101 tracks in total, with tracks 78-101 considered "hidden" tracks. There are also tracks that aren't present during normal gameplay nor in the soundtrack.
The soundtrack is comprised primarily of 23 leitmotifs: Undertale, Your Best Friend (Flowey’s theme), Fallen Down (Toriel’s theme), Ruins / Don't Give Up / An Ending, Uwa!!, Battle / Dogsong / Temmie, Ghost, Determination, Heartache, Sans, Hopes, Papyrus, Undyne, Alphys, Showtime, Mettaton, Another Medium (Hotland’s theme), Oh! One True Love, Glamour (Mettaton EX’s theme), Bergentrückung (Asgore’s theme), Despair, His Theme (Asriel’s theme), and True Hero.
The soundtrack has been widely praised by games press and fans, with Eric Van Allen of GamingTrend saying, "The soundtrack to Undertale reinforces earth-shattering moments, knowing just when to rise and fall, and the frequent use of melodies and themes subconsciously manipulates your heart throughout the whole experience. Each song is reminiscent of a time when melodies had to be simple yet discernible, and each piece finds a way to grow outside the realm of chiptunes without losing that simplicity." Jim Sterling praised the soundtrack as "a damn fine collection of unforgettable tunes." .