The serene sound of a distant music box... It fills you with determination.
Waterfall's SAVE Point before the second encounter with Undyne

Memory is the 34th track in the Undertale Soundtrack.

This music-box melody is the first instance in the game of Asriel's musical theme. The theme appears in other songs at pivotal moments of the game, such as in Undertale (during which the protagonist learns the past of the Dreemurr family), Finale (which provides foreshadowing to Flowey's true identity), and His Theme (when the protagonist saves Asriel).

It first plays from inside the statue of Waterfall, after the protagonist places the umbrella over the statue to shield it from the rain and complete the Piano Puzzle. It also plays later at 70% speed after Undyne attempts to kill the protagonist a second time in Waterfall. While the protagonist is unconscious, they experience a memory of Asriel first meeting the First Human before waking up to find that they have survived yet another fall onto a bed of Golden Flowers.

"Memory" furthermore plays at 80% speed while Undyne reminisces about Asgore during the visit to her house, then when Asgore offers to take care of the protagonist (assuming the protagonist has spared him after fighting him). It is next heard, again at 80% speed, after the fight with Asriel, interestingly continuing very quietly even as Final Power plays and the barrier breaks.

The song plays a final time after the True Pacifist Ending Credits, on the final screen of the game where the Annoying Dog comes to the screen and sleeps. The song does not play if a Genocide Route had been completed for the first time.

The OST version is faster.

Undertale Soundtrack
1 - 10 Once Upon a Time • Start Menu • Your Best Friend • Fallen Down • Ruins
Uwa!! So Temperate♫ • Anticipation • Unnecessary Tension • Enemy Approaching • Ghost Fight
11 - 20 Determination • Home • Home (Music Box) • Heartache • sans.
Nyeh Heh Heh! • Snowy • Uwa!! So Holiday♫ • Dogbass • Mysterious Place
21 - 30 Dogsong • Snowdin Town • Shop • Bonetrousle • Dating Start!
Dating Tense! • Dating Fight! • Premonition • Danger Mystery • Undyne
31 - 40 Waterfall • Run! • Quiet Water • Memory
Bird That Carries You Over A Disproportionately Small Gap • Dummy!
Pathetic House • Spooktune • Spookwave • Ghouliday
41 - 50 Chill • Thundersnail • Temmie Village • Tem Shop • NGAHHH!!
Spear of Justice • Ooo • Alphys • It's Showtime! • Metal Crusher
51 - 60 Another Medium • Uwa!! So HEATS!!♫ • Stronger Monsters • Hotel
Can You Really Call This A Hotel, I Didn't Receive A Mint On My Pillow Or Anything
Confession • Live Report • Death Report • Spider Dance • Wrong Enemy !?
61 - 70 Oh! One True Love • Oh! Dungeon • It's Raining Somewhere Else • CORE Approach • CORE
Last Episode! • Oh My... • Death by Glamour • For The Fans • Long Elevator
71 - 80 Undertale • Song That Might Play When You Fight Sans • The Choice • Small Shock • Barrier
Bergentrückung • ASGORE • You Idiot • Your Best Nightmare • Finale
81 - 90 An Ending • She's Playing Piano • Here We Are • Amalgam • Fallen Down (Reprise)
Don't Give Up • Hopes and Dreams • Burn in Despair! • SAVE the World • His Theme
91 - 100 Final Power • Reunited • Menu (Full) • Respite • Bring It In, Guys! • Last Goodbye
But the Earth Refused to Die • Battle Against a True Hero • Power of "NEO" • MEGALOVANIA
101 Good Night