I've decided to list out every single track included in "Music" but not "My Music." Here are the total tracks for each franchise (Mario, Donkey Kong, Legend of Zelda, etc. aren't included because all their songs are select-able) with 50 total:
- Animal Crossing (6)*
- Super Smash Bros. Series (38)
- Super Smash Bros. (2)
- Super Smash Bros. Melee (5)
- Super Smash Bros. Brawl (10)
- Super Smash Bros. for 3DS/Wii U (10)
- Super Smash Bros. Ultimate (11)
- Splatoon (4)
- Street Fighter (2)
And here are the exact track names for each franchise (ordered alphabetically),
Animal Crossing (6)*:
- K.K. Cruisin'
- K.K. Western
- K.K. Gumbo
- Rockin' K.K.
- DJ K.K.
- K.K. Condor
*Tracks can be played on stage, they just aren't select-able
Super Smash Bros Series (38)
-Super Smash Bros. (2):
- How to Play - Super Smash Bros.
- Menu - Super Smash Bros.
-Super Smash Bros. Melee (5):
- Opening - Super Smash Bros. Melee
- Trophies
- Tournament
- Tournament 2
- All-Star Intro
-Super Smash Bros. Brawl (10):
- Adventure Map
- Step: The Plain
- Step: Subspace
- Home Run Contest
- Trophy Gallery
- Sticker Album/Album/Chronicle
- Tournament Registration
- Tournament Grid
- Tournament Match End
- All-Star Rest Area - Super Smash Bros. Brawl
-Super Smash Bros. for 3DS/Wii U (10):
- Results Screen - Super Smash Bros. for 3DS/Wii U
- Classic: Results Screen
- Classic: Final Results
- Classic: Fail
- Master Core
- Master Fortress: First Wave
- Gallery/Hoard
- Replay/Album/Records
- All-Star Rest Area - Super Smash Bros. for 3DS/Wii U
- StreetSmash
-Super Smash Bros. Ultimate (11):
- Classic Mode: Mural
- Classic Mode: Defeat
- Classic Mode: Final Results
- The Final Battle: After the Transformation
- Free the Spirit!
- Spirits: Collection
- Spirits: Inventory/Items
- Tourney: Battle List
- Tourney: Winner Announcement
- Vault
- Shop
Splatoon (4):
- Now or Never! - Splatoon
- Now or Never! - Splatoon 2
- Now or Never! (Splatfest Version) - Splatoon
- Now or Never! (Splatfest Version) - Splatoon 2
Street Fighter (2):
- Player Select Type A
- Player Select Type B
A couple things to note,
- The reason why the total for the Super Smash Bros. series is 38 and not 33 (like I originally believed) is because there are several tracks included in both Menu and Battlefied/Final Destination under "My Music" such as Mob Smash and The Light Realm: March (I couln't figure out what exactly the others ones were).
- While they cannot be selected, the six Animal Crossing Tracks listed above can be played on Smashville (and I believe Town & City, but I'm not 100% sure), it just depends on the time of day the battle takes place. They cannot be directly selected in "My Music."
Please let me know if you have any questions, or if I made any mistakes. This post took longer than anticipated and I hope the smash community finds it helpful.