Nintendo have been consistently adding to Nintendo Music since the app was first revealed around Halloween last year, slowly expanding the library available from both major releases and those that are a little less well-known.
Their offering this week is Mario Kart 7, which was released on Nintendo 3DS in 2011. A total of 66 tracks from the game have been added.

MK7 for switch online confirmed
How quick will switch 2 soundtrack drops on their would love to see some uploads of world and banaza.
I think almost instantly, Nintendo is going to use that app for promoting new releases no doubt.
Typo in your article, it released on 3DS, not DS👍
I hope they do Mario Kart Double Dash next before doing World.