Undertale Last Breath Canonified OST v2:

OST 01 - Once Upon A Time...

OST 02 - Before the Story...

OST 03 - Menu

OST 04 - Uwa!! So Holiday♫

OST 05 - Determination... (Normal variation)

OST 06 - Frostbite

OST 07 - Dusty Town

OST 08 - Nye heh heh?

OST 09 - Bonetrousle (GENOCIDE)

OST 10 - A truly Trousle!

OST 11 - Enemy Approaching!

OST 12 - Determination... (Snowdin variation)

OST 13 - Menu (Post-Snowdin variation)

OST 14 - Downpour

OST 15 - A Battle Against a True Hero

OST 16 - Boiling Hot

OST 17 - Desolated Hotel

OST 18 - Meltdown

OST 19 - But Nobody Came

OST 20 - Power Of NEO

OST 21 - In My Way

OST 22 - Run!

OST 23 - Determination... (CORE variation)

OST 24 - Menu (Post-core variation)

OST 25 - Memory

OST 26 - Small Shock (GENOCIDE)

OST 27 - Megalomania

OST 28 - Other Song That Might Play When You Fight Sans

OST 29 - There's Still Hopes And...

OST 30 - The SANS-ational Help.

OST 31 - The SANS-ational Help. (Resastered)

OST 32 - Your Best Friend! Right?

OST 33 - You Idiot

OST 34 - Osedax

OST 35 - A True Finale

OST 36 - Determination... (Osedax variation)

OST 37 - Last Goodbye

OST 38 - Menu (Endgame variation)

OST 39 - Extras!

OST 40 - Before the Story... (Endgame variation)

OST 41 - Stronger and Chillier Monsters

OST 42 - A Truly Bonetrousle!

OST 43 - Dog Song

OST 44 - The End...