You can add music to your mashes if you have a Pro subscription.
To do it, follow these quick steps:
To create a mash, tap the Play button at the bottom of your project's screen.
Select "Music" from the mashing options.
To listen to the music, tap on the track's name.
Once you've found the track you want to use, adjust the volume and tap "Done."
iOS app
Android app
If you receive a copyright claim when uploading a mash using the tracks provided by us, please take a look here to learn what you can do.