Nintendo has announced that it has added tracks from Mario Paint, New Super Mario Bros., New Super Mario Bros. Wii, New Super Mario Bros. U, and Super Mario Maker to Mario Kart World‘s Free Roam on the Nintendo Music app for iOS and Android. The Nintendo Music app is a free download and an active Nintendo Switch Online subscription is required to listen to the various soundtracks.
Thanks to Jason F for sending in the news tip!

I have been having a great time in the free roam mode. I just listen to Scott the woz videos while driving around the map and doing p missions, it’s the best!
Right? Truly is the best mode in the game but it would be nice if two player mode in free roam can drive freely on the map through.
I do love the free roam mode in Mario Kart World. Driving around freely by collecting P switches and classic item panels and peach medallions but It’s disappointing that two players can only stick together in free roam sadly.
Kinda wish Nintendo added 3rd party titles or at least do some sort of OST importing from whatever games on the console to the mobile app. Either way the app is much better than it was at launch as it has way more music.