Here is the official playlist of When Last Night Didn't End. Most of these songs describe the emotions of the part they are ascribed to or they exude the general vibe of the story and the characters. A Spotify link is available in an inline comment on this paragraph. Only the Web version lets you click links on comments, so that's that. That playlist is arranged by part as listed here.

Part 1
1. Glimpse of Us - Joji (3:53)
2. Taormina - Laura Di Vaio (2:13)
3. CWJBHN - Jake Scott, Josie Dunne (3:13)
4. Bam Bam - Camila Cabello, Ed Sheeran (3:26)
5. How Do I Say Goodbye - Dean Lewis (2:44)
6. Out of Love - Alessia Cara (3:48)
Total: 19:17

Part 2
1. The Way I Love You - Michal Leah (2:33)
2. Alexandria - Laura Di Vaio (2:39)
3. I Can't Make You Love Me - Colouring (4:37)
4. Enough to Drink - Sam Feldt, Cate Downey (2:18)
5. Good Without - Mimi Webb (3:02)
Total: 15:09

Part 3
1. never knew a heart could break itself - Zach Hood (2:35)
2. golden hour - Piano Version - Pianella Piano (3:32)
3. What Is Loving Anymore - Fiona Harte (3:00)
4. A Potion for Love - AURORA (3:36)
5. that way - Tate McRae, Jeremy Zucker (2:54)
6. Me to You, You to Me - Mido and Falasol (3:52)
Total: 19:32

Part 4
1. emily - Jeremy Zucker, Chelsea Cutler (3:54)
2. Siena - Laura Di Vaio (2:25)
3. The Good Parts - JP Saxe (3:18)
4. June - Sage Charmaine (3:03)
5. go - Cat Burns (3:35)
Total: 16:15

Part 5
1. Bla Bli Blu - Valentina Ploy (2:58)
2. Deep Rivers - Laura Di Vaio (2:16)
3. The Night We Met - Lord Huron, Phoebe Bridgers (3:28)
4. fOoL fOr YoU - ZAYN (3:22)
5. all i need (the distance song) - Avery Lynch (4:04)
Total: 16:08

Part 6
1. Maroon - Taylor Swift (3:38)
2. Falling Slowly - Charles Weathersby (3:18)
3. Anti-Hero - Acoustic Version - Taylor Swift (3:16)
4. Dancing With Your Ghost - Sasha Alex Sloan (3:18)
5. Highs & Lows - Alexander Jean (3:35)
6 Christmas Tree - V (3:30)
Total: 20:35

Part 7
1. Until I Found You - Stephen Sanchez (2:58)
2. Etérea - Laura Di Vaio (2:27)
3. Turbulence - Emma Charles (2:44)
4. What a Time - Julia Michaels, Niall Horan (2:53)
5. Easy - Camila Cabello (3:15)
Total: 14:17

Part 8
1. Could I Love You Anymore - Reneé Dominique, Jason Mraz (3:10)
2. February 1, 2023: C/2022 E3 - Comet Ztf - Sleeping At Last (3:12)
3. Poets - Gallipoli (2:57)
4. The Great War - Taylor Swift (4:00)
5. Message in a Bottle (Taylor's Version) - Taylor Swift (3:46)
6. Your Ocean - Hoppipolla (4:46)
Total: 21:51

Part 9
1. Hold Me Closer - Cornelia Jakobs (3:19)
2. rebind - Instrumental - TRUE (4:42)
3. Two - Sleeping At Last (4:19)
4. The Way You Look At Me - Ben&Ben (4:12)
5. Reckless - Madison Beer (3:23)
6. Freezing - Mimi Webb (2:57)
Total: 22:52

Part 10
1. Losing Me - Gabrielle Aplin, JP Cooper (3:10)
2. Atom 9 - Sleeping At Last (1:02)
3. Young and Beautiful - Acoustic - Honeyfox, lost., Pop Mage (3:30)
4. One of Us - Ava Max (2:58)
5. lovely - Billie Eilish, Khalid (3:20)
6. Kids in Love - P!nk, First Aid Kit (2:47)
Total: 16:47

Part 11
1. Yours Tomorrow - Winona Oak (2:32)
2. Dédalo - Laura Di Vaio (2:02)
3. Die Together - Amanda Tenfjord (2:55)
4. The Ones We Ones Loved - Ben&Ben (4:33)
5. This is Me Letting You Go - Lukas Graham (2:50)
6. To Be Enchanted - Sleeping At Last (3:10)
Total: 18:02

Part 12
1. Oceans & Engines - NIKI (5:36)
2. Love you to the moon and back - Touch of Love (1:39)
3. Die For You - LÉON (3:37)
4. Butterflies - Tom Odell, AURORA (2:11)
5. Missing You - Stephen Sanches, Ashe (3:56)
6. Maybe in the Morning - Zach Seabaugh, Anna Hamilton (2:44)
Total: 19:43