Unused Mario kart 7 menu theme by MDHEXT at 5:48 AM EDT on July 16, 2019
I'm not sure where to look for it, but it was ripped by someone and I still don't know where the music is located. It isn't the download play theme and I know that the only place it could be is in the bcsar file, but I don't know how to proceed beyond this.
unpacking the bcsar file using VGMToolbox should help. go to offset finder and type the name of the bcsar file, load the 3DS CWAV mode (next to the drag and drop box) and select "load"
select the destination folder and drag and drop the file in the (name of the file you typed) box.
you may get thousands of CWAVs, which you can convert using VGSC.